Frequency of Mutations in the TPO Gene in Patients with Congenital Hypothyroidism Due to Dyshormonogenesis in Chile.

Background and Objectives: Congenital thyroid dyshormonogenesis is caused by alterations in the synthesis of thyroid hormones in a newborn. Additionally, 10 to 20% of these cases are hereditary, caused by defects in proteins involved in hormonal synthesis. One of the most common causes is mutations in the thyroid peroxidase (TPO) enzyme gene, an autosomal recessive disease. We aimed to detect mutations of the TPO gene in 12 Chilean patients with congenital hypothyroidism due to dyshormonogenesis (CHD) and to characterize these patients clinically and molecularly. Materials and Methods: Twelve patients under 20 years of age with CHD, controlled at San Juan de Dios Hospital in Santiago, Chile, were selected according to the inclusion criteria: elevated neonatal TSH, persistent hypothyroidism, and thyroid normotopic by imaging study. Those with deafness, Down syndrome, and central or transient congenital hypothyroidism were excluded. Blood samples were taken for DNA extraction, and the 17 exons and exon-intron junctions of the TPO gene were amplified by PCR. The PCR products were sequenced by Sanger. Results: Two possibly pathogenic mutations of the TPO gene were detected: c.2242G>A (p.Val748Met) and c.1103C>T (p.Pro368Leu). These mutations were detected in 2 of 12 patients (16.6%): 1 was compound heterozygous c.1103C>T/c.2242G>A, and the other was heterozygous for c.2242G>A. In the diagnostic confirmation test, both patients presented diffuse hyper-uptake goiter on thyroid scintigraphy and high TSH in venous blood (>190 uIU/mL). Conclusions: The frequency of patients with possibly pathogenic mutations in TPO with CHD was 16.6%. Its study would allow for genetic counseling to be offered to the families of affected patients.

DNA Base Damage Repair Crosstalks with Chromatin Structures to Contract Expanded GAA Repeats in Friedreich's Ataxia.

Trinucleotide repeat (TNR) expansion is the cause of over 40 neurodegenerative diseases, including Huntington's disease and Friedreich's ataxia (FRDA). There are no effective treatments for these diseases due to the poor understanding of molecular mechanisms underlying somatic TNR expansion and contraction in neural systems. We and others have found that DNA base excision repair (BER) actively modulates TNR instability, shedding light on the development of effective treatments for the diseases by contracting expanded repeats through DNA repair. In this study, temozolomide (TMZ) was employed as a model DNA base damaging agent to reveal the mechanisms of the BER pathway in modulating GAA repeat instability at the frataxin (FXN) gene in FRDA neural cells and transgenic mouse mice. We found that TMZ induced large GAA repeat contraction in FRDA mouse brain tissue, neurons, and FRDA iPSC-differentiated neural cells, increasing frataxin protein levels in FRDA mouse brain and neural cells. Surprisingly, we found that TMZ could also inhibit H3K9 methyltransferases, leading to open chromatin and increasing ssDNA breaks and recruitment of the key BER enzyme, pol ß, on the repeats in FRDA neural cells. We further demonstrated that the H3K9 methyltransferase inhibitor BIX01294 also induced the contraction of the expanded repeats and increased frataxin protein in FRDA neural cells by opening the chromatin and increasing the endogenous ssDNA breaks and recruitment of pol ß on the repeats. Our study provides new mechanistic insight illustrating that inhibition of H3K9 methylation can crosstalk with BER to induce GAA repeat contraction in FRDA. Our results will open a new avenue for developing novel gene therapy by targeting histone methylation and the BER pathway for repeat expansion diseases.

[New Drug Discovery Targeting Iron in Bacterial Infectious Diseases].

Iron is necessary for all living organisms, and bacteria that cause infections in human hosts also need ferrous ions for their growth and proliferation. In the human body, most ferric ions (Fe3+) are tightly bound to iron-binding proteins such as hemoglobin, transferrin, lactoferrin, and ferritin. Pathogenic bacteria express highly specific iron uptake systems, including siderophores and specific receptors. Most bacteria secrete siderophores, which are low-molecular weight metal-chelating agents, to capture Fe3+ outside cell. Siderophores are mainly classified as either catecholate or hydroxamate. Vibrio vulnificus, a Gram-negative pathogenic bacterium, is responsible for serious infections in humans and requires iron for growth. A clinical isolate, V. vulnificus M2799, secretes a catecholate siderophore, vulnibactin, that captures ferric ions from the environment. In our study, we generated deletion mutants of the genes encoding proteins involved in the vulnibactin mediated iron-utilization system, such as ferric-vulnibactin receptor protein (VuuA), periplasmic ferric-vulnibactin binding protein (FatB), ferric-vulnibactin reductase (VuuB), and isochorismate synthase (ICS). ICS and VuuA are required under low-iron conditions for ferric-utilization in M2799, but the alternative proteins FatB and VuuB can function as a periplasmic binding protein and a ferric-chelate reductase, respectively. VatD, which functions as ferric-hydroxamate siderophores periplasmic binding protein, was shown to participate in the ferric-vulnibactin uptake system in the absence of FatB. Furthermore, the ferric-hydroxamate siderophore reductase IutB was observed to participate in ferric-vulnibactin reduction in the absence of VuuB. We propose that ferric-siderophore periplasmic binding proteins and ferric-chelate reductases represent potential targets for drug discovery in the context of infectious diseases.

The binding pattern of ferric iron and iron-binding protein in Botrytis cinerea.

Iron-binding protein (Ibp) has protective effect on pathogen exposed to H2O2 in defense response of plants. Ibp in Botrytis cinerea (BcIbp) is related to its virulence. Bcibp mutation lead to virulence deficiencies in B. cinerea. BcIbp is involved in the Fe3+ homeostasis regulation. Recognition the binding site and binding pattern of ferric iron and iron-binding protein in B. cinerea are vital to understand its function. In this study, molecular dynamics (MD) simulations, gaussian accelerated molecular dynamics (GaMD) simulations, dynamic cross correlation analysis and quantum chemical energy calculation were used to explore binding pattern of ferric iron. MD results showed that the C-terminal region had little effect on the stability of residues in the Fe3+-binding pocket. Energy calculations suggested the most likely coordination pattern for ferric iron in iron-binding protein. These results will help to understand the binding of ferric iron to iron-binding protein and provide new ideas for regulating the virulence of B. cinerea.

An In Silico Analysis of Genetic Variants and Structural Modeling of the Human Frataxin Protein in Friedreich's Ataxia.

Friedreich's Ataxia (FRDA) stands out as the most prevalent form of hereditary ataxias, marked by progressive movement ataxia, loss of vibratory sensitivity, and skeletal deformities, severely affecting daily functioning. To date, the only medication available for treating FRDA is Omaveloxolone (Skyclarys®), recently approved by the FDA. Missense mutations within the human frataxin (FXN) gene, responsible for intracellular iron homeostasis regulation, are linked to FRDA development. These mutations induce FXN dysfunction, fostering mitochondrial iron accumulation and heightened oxidative stress, ultimately triggering neuronal cell death pathways. This study amalgamated 226 FXN genetic variants from the literature and database searches, with only 18 previously characterized. Predictive analyses revealed a notable prevalence of detrimental and destabilizing predictions for FXN mutations, predominantly impacting conserved residues crucial for protein function. Additionally, an accurate, comprehensive three-dimensional model of human FXN was constructed, serving as the basis for generating genetic variants I154F and W155R. These variants, selected for their severe clinical implications, underwent molecular dynamics (MD) simulations, unveiling flexibility and essential dynamic alterations in their N-terminal segments, encompassing FXN42, FXN56, and FXN78 domains pivotal for protein maturation. Thus, our findings indicate potential interaction profile disturbances in the FXN42, FXN56, and FXN78 domains induced by I154F and W155R mutations, aligning with the existing literature.

The Regulation of the Disease-Causing Gene FXN.

Friedreich's ataxia (FRDA) is a progressive neurodegenerative disease caused in almost all patients by expanded guanine-adenine-adenine (GAA) trinucleotide repeats within intron 1 of the FXN gene. This results in a relative deficiency of frataxin, a small nucleus-encoded mitochondrial protein crucial for iron-sulfur cluster biogenesis. Currently, there is only one medication, omaveloxolone, available for FRDA patients, and it is limited to patients 16 years of age and older. This necessitates the development of new medications. Frataxin restoration is one of the main strategies in potential treatment options as it addresses the root cause of the disease. Comprehending the control of frataxin at the transcriptional, post-transcriptional, and post-translational stages could offer potential therapeutic approaches for addressing the illness. This review aims to provide a general overview of the regulation of frataxin and its implications for a possible therapeutic treatment of FRDA.

Identification of southern Taiwan genetic variants in thyroid dyshormonogenesis through whole-exome sequencing.

Thyroid dyshormonogenesis (TDH) is responsible for 15%-25% of congenital hypothyroidism (CH) cases. Pathogenetic variants of this common inherited endocrine disorders vary geographically. Unraveling the genetic underpinnings of TDH is essential for genetic counseling and precise therapeutic strategies. This study aims to identify genetic variants associated with TDH in Southern Taiwan using whole exome sequencing (WES). We included CH patients diagnosed through newborn screening at a tertiary medical center from 2011 to 2022. Permanent TDH was determined based on imaging evidence of bilateral thyroid structure and the requirement for continuous medication beyond 3 years of age. Genomic DNA extracted from blood was used for exome library construction, and pathogenic variants were detected using an in-house algorithm. Of the 876 CH patients reviewed, 121 were classified as permanent, with 47 (40%) confirmed as TDH. WES was conducted for 45 patients, and causative variants were identified in 32 patients (71.1%), including DUOX2 (15 cases), TG (8 cases), TSHR (7 cases), TPO (5 cases), and DUOXA2 (1 case). Recurrent variants included DUOX2 c.3329G>A, TSHR c.1349G>A, TG c.1348delT, and TPO c.2268dupT. We identified four novel variants based on genotype, including TSHR c.1135C>T, TSHR c.1349G>C, TG c.2461delA, and TG c.2459T>A. This study underscores the efficacy of WES in providing definitive molecular diagnoses for TDH. Molecular diagnoses are instrumental in genetic counseling, formulating treatment, and developing management strategies. Future research integrating larger population cohorts is vital to further elucidate the genetic landscape of TDH.

Determination of the levels and possible associations of alpha2-macroglobulin with autoantibodies in the serum of patients with various forms of autoimmune thyroiditis.

Antibodies to thyroid peroxidase (AB-TPO), antibodies to thyroglobulin (AB-TG), and the content of α2-macroglobulin (α2-MG) have been studied in serum samples of patients with autoimmune thyroiditis (AIT). All the patients were divided into 3 groups depending on age: 25-35, 36-50, 51-65 years. We found a significant change in the thyroid panel parameters in AIT, but without significant changes in the average concentration of α2-MG in the age groups of patients. This may be due to the accumulation and retention of complexes of defective forms of α2-MG in the circulation associated with their decreased ability to bind to receptors.

Calcitriol Treatment Is Safe and Increases Frataxin Levels in Friedreich Ataxia Patients.

BACKGROUND: Calcitriol, the active form of vitamin D (also known as 1,25-dihydroxycholecalciferol), improves the phenotype and increases frataxin levels in cell models of Friedreich ataxia (FRDA). OBJECTIVES: Based on these results, we aimed measuring the effects of a calcitriol dose of 0.25 mcg/24h in the neurological function and frataxin levels when administered to FRDA patients for a year. METHODS: 20 FRDA patients where recluted and 15 patients completed the treatment for a year. Evaluations of neurological function changes (SARA scale, 9-HPT, 8-MWT, PATA test) and quality of life (Barthel Scale and Short Form (36) Health Survey [SF-36] quality of life questionnaire) were performed. Frataxin amounts were measured in isolated platelets obtained from these FRDA patients, from heterozygous FRDA carriers (relatives of the FA patients) and from non-heterozygous sex and age matched controls. RESULTS: Although the patients did not experience any observable neurological improvement, there was a statistically significant increase in frataxin levels from initial values, 5.5 to 7.0 pg/µg after 12 months. Differences in frataxin levels referred to total protein levels were observed among sex- and age-matched controls (18.1 pg/µg), relative controls (10.1 pg/µg), and FRDA patients (5.7 pg/µg). The treatment was well tolerated by most patients, and only some of them experienced minor adverse effects at the beginning of the trial. CONCLUSIONS: Calcitriol dosage used (0.25 mcg/24 h) is safe for FRDA patients, and it increases frataxin levels. We cannot rule out that higher doses administered longer could yield neurological benefits. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

In vitro assessment of thyroid peroxidase inhibition by chemical exposure: comparison of cell models and detection methods.

Disruption of the thyroid hormone (TH) system is connected with diverse adverse health outcomes in wildlife and humans. It is crucial to develop and validate suitable in vitro assays capable of measuring the disruption of the thyroid hormone (TH) system. These assays are also essential to comply with the 3R principles, aiming to replace the ex vivo tests often utilised in the chemical assessment. We compared the two commonly used assays applicable for high throughput screening [Luminol and Amplex UltraRed (AUR)] for the assessment of inhibition of thyroid peroxidase (TPO, a crucial enzyme in TH synthesis) using several cell lines and 21 compounds from different use categories. As the investigated cell lines derived from human and rat thyroid showed low or undetectable TPO expression, we developed a series of novel cell lines overexpressing human TPO protein. The HEK-TPOA7 model was prioritised for further research based on the high and stable TPO gene and protein expression. Notably, the Luminol assay detected significant peroxidase activity and signal inhibition even in Nthy-ori 3-1 and HEK293T cell lines without TPO expression, revealing its lack of specificity. Conversely, the AUR assay was specific to TPO activity. Nevertheless, despite the different specificity, both assays identified similar peroxidation inhibitors. Over half of the tested chemicals with diverse structures and from different use groups caused TPO inhibition, including some widespread environmental contaminants suggesting a potential impact of environmental chemicals on TH synthesis. Furthermore, in silico SeqAPASS analysis confirmed the high similarity of human TPO across mammals and other vertebrate classes, suggesting the applicability of HEK-TPOA7 model findings to other vertebrates.

Ferrostatin-1 specifically targets mitochondrial iron-sulfur clusters and aconitase to improve cardiac function in Sirtuin 3 cardiomyocyte knockout mice.

AIMS: Ferroptosis is a form of iron-regulated cell death implicated in ischemic heart disease. Our previous study revealed that Sirtuin 3 (SIRT3) is associated with ferroptosis and cardiac fibrosis. In this study, we tested whether the knockout of SIRT3 in cardiomyocytes (SIRT3cKO) promotes mitochondrial ferroptosis and whether the blockade of ferroptosis would ameliorate mitochondrial dysfunction. METHODS AND RESULTS: Mitochondrial and cytosolic fractions were isolated from the ventricles of mice. Cytosolic and mitochondrial ferroptosis were analyzed by comparison to SIRT3loxp mice. An echocardiography study showed that SIRT3cKO mice developed heart failure as evidenced by a reduction of EF% and FS% compared to SIRT3loxp mice. Comparison of mitochondrial and cytosolic fractions of SIRT3cKO and SIRT3loxp mice revealed that, upon loss of SIRT3, mitochondrial, but not cytosolic, total lysine acetylation was significantly increased. Similarly, acetylated p53 was significantly upregulated only in the mitochondria. These data demonstrate that SIRT3 is the primary mitochondrial deacetylase. Most importantly, loss of SIRT3 resulted in significant reductions of frataxin, aconitase, and glutathione peroxidase 4 (GPX4) in the mitochondria. This was accompanied by a significant increase in levels of mitochondrial 4-hydroxynonenal. Treatment of SIRT3cKO mice with the ferroptosis inhibitor ferrostatin-1 (Fer-1) for 14 days significantly improved preexisting heart failure. Mechanistically, Fer-1 treatment significantly increased GPX4 and aconitase expression/activity, increased mitochondrial iron­sulfur clusters, and improved mitochondrial membrane potential and Complex IV activity. CONCLUSIONS: Inhibition of ferroptosis ameliorated cardiac dysfunction by specifically targeting mitochondrial aconitase and iron­sulfur clusters. Blockade of mitochondrial ferroptosis may be a novel therapeutic target for mitochondrial cardiomyopathies.

Sex-Specific Associations between Maternal Thyroid Peroxidase Antibodies and Cognitive Development in Preschool Children: A Prospective Cohort Study.

Background: An association between maternal thyroid dysfunction throughout pregnancy and the subsequent risk of neurodevelopmental abnormalities in offspring has been demonstrated. However, the potential effects of maternal thyroid autoimmunity on neurodevelopment in the absence of maternal hypothyroidism remain unclear. Therefore, in this study, we explored the association between maternal thyroid peroxidase antibody (TPOAb) positivity and cognitive development in preschool children. Methods: A total of 1849 mother-child pairs were recruited from the Ma'anshan Birth Cohort (MABC) Study. During the follow-up period, an electrochemiluminescence immunoassay was used to retrospectively measure serum TPOAb levels in pregnant women. The cognitive development of preschool children was evaluated by using the Chinese version of the Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition (WPPSI-IV). A growth mixture model was used to fit the trajectory of TPOAb. Multiple linear regression and logistic regression models were used to explore the associations between the developmental trajectory of TPOAb-positivity at different gestational periods and the cognitive development of preschool children by sex. Results: A total of 1849 mother-child pairs (mean [SD] age: 26.7 [3.6] years) were enrolled in the final study. Maternal TPOAb positivity in the first trimester was associated with a risk of below-average processing speed index in girls (OR: 2.07; 95% CI 1.06 to 4.01) and below-average full-scale intelligence quotient (FSIQ) in boys (OR: 2.36; 95% CI: 1.10 to 5.05). Maternal TPOAb positivity in the third trimester (T3) was associated with below-average working memory index (WMI) (OR: 2.51; 95% CI: 1.02 to 6.20) in girls. In girls, the WMI (ß = -3.17, 95% CI: -5.82 to -0.52), fluid reasoning index (FRI) (ß = -4.49, 95% CI: -7.18 to -1.80), and FSIQ score (ß = -2.43, 95% CI: -4.77 to -0.08) decreased, whereas in mothers, the level of log-transformed thyroid peroxidase antibody (lgTPOAb) increased during pregnancy. Conclusions: Positive maternal TPOAb levels during pregnancy may be associated with poorer cognitive development in preschool children. These findings require independent confirmation in other populations.

Pharmacotherapeutic strategies for Friedreich Ataxia: a review of the available data.

INTRODUCTION: Friedreich ataxia (FRDA) is a rare autosomal recessive disease, marked by loss of coordination as well as impaired neurological, endocrine, orthopedic, and cardiac function. There are many symptomatic medications for FRDA, and many clinical trials have been performed, but only one FDA-approved medication exists. AREAS COVERED: The relative absence of the frataxin protein (FXN) in FRDA causes mitochondrial dysfunction, resulting in clinical manifestations. Currently, the only approved treatment for FRDA is an Nrf2 activator called omaveloxolone (Skyclarys). Patients with FRDA also rely on various symptomatic medications for treatment. Because there is only one approved medication for FRDA, clinical trials continue to advance in FRDA. Although some trials have not met their endpoints, many current and upcoming clinical trials provide exciting possibilities for the treatment of FRDA. EXPERT OPINION: The approval of omaveloxolone provides a major advance in FRDA therapeutics. Although well tolerated, it is not curative. Reversal of deficient frataxin levels with gene therapy, protein replacement, or epigenetic approaches provides the most likely prospect for enduring, disease-modifying therapy in the future.

Expression and processing of mature human frataxin after gene therapy in mice.

Friedreich's ataxia is a degenerative and progressive multisystem disorder caused by mutations in the highly conserved frataxin (FXN) gene that results in FXN protein deficiency and mitochondrial dysfunction. While gene therapy approaches are promising, consistent induction of therapeutic FXN protein expression that is sub-toxic has proven challenging, and numerous therapeutic approaches are being tested in animal models. FXN (hFXN in humans, mFXN in mice) is proteolytically modified in mitochondria to produce mature FXN. However, unlike endogenous hFXN, endogenous mFXN is further processed into N-terminally truncated, extra-mitochondrial mFXN forms of unknown function. This study assessed mature exogenous hFXN expression levels in the heart and liver of C57Bl/6 mice 7-10 months after intravenous administration of a recombinant adeno-associated virus encoding hFXN (AAVrh.10hFXN) and examined the potential for hFXN truncation in mice. AAVrh.10hFXN induced dose-dependent expression of hFXN in the heart and liver. Interestingly, hFXN was processed into truncated forms, but found at lower levels than mature hFXN. However, the truncations were at different positions than mFXN. AAVrh.10hFXN induced mature hFXN expression in mouse heart and liver at levels that approximated endogenous mFXN levels. These results suggest that AAVrh.10hFXN can likely induce expression of therapeutic levels of mature hFXN in mice.

[Molecular mimicry between human thyroid peroxidase, thyroglobulin, cosinophil peroxidase, IL-24 and microorganisms antigens]. / Mimetismo molecular entre peroxidasa tiroidea humana, tiroglobulina, peroxidasa de eosinófilos, IL-24 y antígenos de microorganismos.

OBJECTIVE: Identify molecular mimicry between TPO, eosinophil peroxidase (EPX), thyroglobulin and IL24 and microorganism antigens. METHODS: Through in silico analysis, we performed local alignments between human and microorganism antigens with PSI-BLAST. Proteins that did not present a 3D structure were modeled by homology through the Swiss Modeller server and epitope prediction was performed through Ellipro. Epitopes were located in the 3D models using PYMOL software. RESULTS: A total of 38 microorganism antigens (parasites, bacteria) had identities between 30% and 45%, being the highest with Anisakis simplex. The alignment between 2 candidate proteins from A. simplex and EPX presented significant values, with identities of 43 and 44%. In bacteria, Campylobacter jejuni presented the highest identity with thyroglobulin (35%). 220 linear and conformational epitopes of microorganism antigens were predicted. Peroxidasin-like proteins from Toxocara canis and Trichinella pseudospiralis presented 10 epitopes similar to TPO and EPX, as possible molecules triggering cross-reactivity. No virus presented identity with the human proteins studied. CONCLUSION: TPO and EPX antigens shared potential cross-reactive epitopes with bacterial and nematode proteins, suggesting that molecular mimicry could be a mechanism that explains the relationship between infections and urticaria/hypothyroidism. In vitro work is needed to demonstrate the results obtained in the in silico analysis.

OBJETIVO: Identificar mimetismo molecular entre TPO, eosinofil peroxidasa (EPX), tiroglobulina e IL24 y antígenos de microorganismos. MÉTODOS: A través de análisis in silico, realizamos los alineamientos locales entre los antígenos humanos y de microorganismos con PSI-BLAST. Las proteínas que no presentaban estructura 3D, fueron modeladas por homología a través del servidor Swiss Modeller y se realizó una predicción de epítopes a través de Ellipro. Los epítopes se localizaron en los modelos 3D utilizando el software PYMOL. RESULTADOS: Un total de 38 antígenos de microorganismos (parásitos y bacterias), tuvieron identidades entre 30 y 45%, siendo los más altos con Anisakis simplex. El alineamiento entre dos proteínas candidatas de A. simplex y EPX presentaron valores importantes, con identidades de 43 y 44%. En las bacterias, Campylobacter jejuni presentó la mayor identidad con tiroglobulina (35%). Se predijeron 220 epítopes lineales y conformacionales de antígenos de microorganismos. Las proteínas similares a la peroxidasina de Toxocara canis y Trichinella pseudospiralis presentaron diez epítopes similares a TPO y EPX, como posibles moléculas desencadenantes de una reactividad cruzada. Ningún virus presentó identidad con las proteínas humanas estudiadas. CONCLUSIÓN: Los antígenos TPO y EPX compartieron potenciales epítopes de reacción cruzada con proteínas bacterianas y nematodos, lo que sugiere que el mimetismo molecular podría ser un mecanismo que explique la relación entre infecciones y la urticaria/hipotiroidismo. Se necesitan trabajos in vitro que demuestren los resultados obtenidos en el análisis in silico.

Expression, purification and preliminary crystallographic analysis of bacterial transmembrane protein EfeU for iron import.

The bacterial Efe system functions as an importer of free Fe2+ into cells independently of iron-chelating compounds such as siderophores and consisted of iron-binding protein EfeO, peroxidase EfeB, and transmembrane permease EfeU. While we and other researchers reported crystal structures of EfeO and EfeB, that of EfeU remains undetermined. In this study, we constructed expression system of EfeU derived from Escherichia coli, selected E. coli Rosetta-gami 2 (DE3) as an expression host, and succeeded in purification of the proteins which were indicated to form an oligomer by blue native PAGE. We obtained preliminary data of the X-ray crystallography, suggesting that expression and purification methods we established in this study enable structural analysis of the bacterial Efe system.

Mechanism and structural dynamics of sulfur transfer during de novo [2Fe-2S] cluster assembly on ISCU2.

Maturation of iron-sulfur proteins in eukaryotes is initiated in mitochondria by the core iron-sulfur cluster assembly (ISC) complex, consisting of the cysteine desulfurase sub-complex NFS1-ISD11-ACP1, the scaffold protein ISCU2, the electron donor ferredoxin FDX2, and frataxin, a protein dysfunctional in Friedreich's ataxia. The core ISC complex synthesizes [2Fe-2S] clusters de novo from Fe and a persulfide (SSH) bound at conserved cluster assembly site residues. Here, we elucidate the poorly understood Fe-dependent mechanism of persulfide transfer from cysteine desulfurase NFS1 to ISCU2. High-resolution cryo-EM structures obtained from anaerobically prepared samples provide snapshots that both visualize different stages of persulfide transfer from Cys381NFS1 to Cys138ISCU2 and clarify the molecular role of frataxin in optimally positioning assembly site residues for fast sulfur transfer. Biochemical analyses assign ISCU2 residues essential for sulfur transfer, and reveal that Cys138ISCU2 rapidly receives the persulfide without a detectable intermediate. Mössbauer spectroscopy assessing the Fe coordination of various sulfur transfer intermediates shows a dynamic equilibrium between pre- and post-sulfur-transfer states shifted by frataxin. Collectively, our study defines crucial mechanistic stages of physiological [2Fe-2S] cluster assembly and clarifies frataxin's molecular role in this fundamental process.

Disulfide Bonds of Thyroid Peroxidase Are Critical Elements for Subcellular Localization, Proteasome-Dependent Degradation, and Enzyme Activity.

Background: Congenital hypothyroidism (CH) is caused by mutations in cysteine residues, including Cys655 and Cys825 that form disulfide bonds in thyroid peroxidase (TPO). It is highly likely that these disulfide bonds could play an important role in TPO activity. However, to date, no study has comprehensively analyzed cysteine mutations that form disulfide bonds in TPO. In this study, we induced mutations in cysteine residues involved in disulfide bonds formation and analyzed their effect on subcellular localization, degradation, and enzyme activities to evaluate the importance of disulfide bonds in TPO activity. Methods: Vector plasmid TPO mutants, C655F and C825R, known to occur in CH, were transfected into HEK293 cells. TPO activity and protein expression levels were measured by the Amplex red assay and Western blotting. The same procedure was performed in the presence of MG132 proteasome inhibitor. Subcellular localization was determined using immunocytochemistry and flow cytometry. The locations of all disulfide bonds within TPO were predicted using in silico analysis. All TPO mutations associated with disulfide bonds were induced. TPO activity and protein expression levels were also measured in all TPO mutants associated with disulfide bonds using the Amplex red assay and Western blotting. Results: C655F and C825R showed significantly decreased activity and protein expression compared with the wild type (WT) (p < 0.05). In the presence of the MG132 proteasome inhibitor, the protein expression level of TPO increased to a level comparable with that of the WT without increases in its activity. The degree of subcellular distribution of TPO to the cell surface in the mutants was lower compared with the WT TPO. Twenty-four cysteine residues were involved in the formation of 12 disulfide bonds in TPO. All TPO mutants harboring an amino acid substitution in each cysteine showed significantly reduced TPO activity and protein expression levels. Furthermore, the differences in TPO activity depended on the position of the disulfide bond. Conclusions: All 12 disulfide bonds play an important role in the activity of TPO. Furthermore, the mutations lead to misfolding, degradation, and membrane insertion.

Generation and characterization of iPSC lines from Friedreich's ataxia patient (FRDA) with GAA.TTC repeat expansion in the Frataxin (FXN) gene's first intron (IGIBi016-A) and a non-FRDA healthy control individual (IGIBi017-A).

Friedreich's ataxia is a spinocerebellar degenerative disease caused by microsatellite (GAA.TTC)n repeat expansion in the first intron of FXN gene. Here, we developed iPSC lines from an FRDA patient (IGIBi016-A) and non-FRDA healthy control (IGIBi017-A). Both iPSC lines displayed typical iPSC morphology, expression of pluripotency markers, regular karyotypes (46, XY; 46, XX), capacity to grow into three germ layers, and FRDA hallmark -GAA repeat expansion and decreased FXN mRNA. Through these iPSC lines, FRDA phenotypes may be replicated in the in vitro assays, by creating neuron subtypes, cardiomyocytes and 3D organoids, for molecular and cellular biomarkers and therapeutic applications.

Inhibition of CISD1 attenuates cisplatin-induced hearing loss in mice via the PI3K and MAPK pathways.

Cisplatin is an effective chemotherapeutic drug for different cancers, but it also causes severe and permanent hearing loss. Oxidative stress and mitochondrial dysfunction in cochlear hair cells (HCs) have been shown to be important in the pathogenesis of cisplatin-induced hearing loss (CIHL). CDGSH iron sulfur domain 1 (CISD1, also known as mitoNEET) plays a critical role in mitochondrial oxidative capacity and cellular bioenergetics. Targeting CISD1 may improve mitochondrial function in various diseases. However, the role of CISD1 in cisplatin-induced ototoxicity is unclear. Therefore, this study was performed to assess the role of CISD1 in cisplatin-induced ototoxicity. We found that CISD1 expression was significantly increased after cisplatin treatment in both HEI-OC1 cells and cochlear HCs. Moreover, pharmacological inhibition of CISD1 with NL-1 inhibited cell apoptosis and reduced mitochondrial reactive oxygen species accumulation in HEI-OC1 cells and cochlear explants. Inhibition of CISD1 with small interfering RNA in HEI-OC1 cells had similar protective effects. Furthermore, NL-1 protected against CIHL in adult C57 mice, as evaluated by the auditory brainstem response and immunofluorescent staining. Mechanistically, RNA sequencing revealed that NL-1 attenuated CIHL via the PI3K and MAPK pathways. Most importantly, NL-1 did not interfere with the antitumor efficacy of cisplatin. In conclusion, our study revealed that targeting CISD1 with NL-1 reduced reactive oxygen species accumulation, mitochondrial dysfunction, and apoptosis via the PI3K and MAPK pathways in HEI-OC1 cell lines and mouse cochlear explants in vitro, and it protected against CIHL in adult C57 mice. Our study suggests that CISD1 may serve as a novel target for the prevention of CIHL.