51
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Cochaperone binding to LYR motifs confers specificity of iron sulfur cluster delivery. Cell Metab 2014; 19:445-57. [PMID: 24606901 PMCID: PMC6550293 DOI: 10.1016/j.cmet.2014.01.015] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 12/12/2013] [Accepted: 01/22/2014] [Indexed: 11/22/2022]
Abstract
Iron sulfur (Fe-S) clusters, preassembled on the ISCU scaffold, are transferred to target proteins or to intermediate scaffolds by a dedicated chaperone-cochaperone system. However, the molecular mechanisms that underlie substrate discrimination and guide delivery of nascent clusters to specific subsets of Fe-S recipients are poorly understood. Here, we identified interacting partners of the cochaperone HSC20 and discovered that LYR motifs are molecular signatures of specific recipient Fe-S proteins or accessory factors that assist Fe-S cluster delivery. In succinate dehydrogenase B, two LYR motifs engage the ISCU-HSC20-HSPA9 complex to aid incorporation of three Fe-S clusters within the final structure of complex II. Moreover, we show that members of the LYR motif family which assist assembly of complexes II or III, SDHAF1 and LYRM7, respectively, are HSC20 binding partners. Our studies unveil a network of interactions between HSC20 and LYR motif-containing proteins that are key to the assembly and function of complexes I, II, and III.
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52
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Abstract
How are nascent iron-sulfur (Fe-S) clusters directed to specific recipient proteins? In this issue of Cell Metabolism, Maio et al. (2014) show that the mitochondrial Fe-S cochaperone protein HSC20 guides nascent Fe-S clusters based on a highly conserved motif, LYR, that exists in target proteins in different molecular contexts.
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Affiliation(s)
- D J R Lane
- Department of Pathology and Bosch Institute, Molecular Pharmacology and Pathology Program, Blackburn Building, University of Sydney, Sydney, NSW 2006, Australia.
| | - A M Merlot
- Department of Pathology and Bosch Institute, Molecular Pharmacology and Pathology Program, Blackburn Building, University of Sydney, Sydney, NSW 2006, Australia
| | - D R Richardson
- Department of Pathology and Bosch Institute, Molecular Pharmacology and Pathology Program, Blackburn Building, University of Sydney, Sydney, NSW 2006, Australia.
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53
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Saha PP, Kumar SKP, Srivastava S, Sinha D, Pareek G, D'Silva P. The presence of multiple cellular defects associated with a novel G50E iron-sulfur cluster scaffold protein (ISCU) mutation leads to development of mitochondrial myopathy. J Biol Chem 2014; 289:10359-10377. [PMID: 24573684 DOI: 10.1074/jbc.m113.526665] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Iron-sulfur (Fe-S) clusters are versatile cofactors involved in regulating multiple physiological activities, including energy generation through cellular respiration. Initially, the Fe-S clusters are assembled on a conserved scaffold protein, iron-sulfur cluster scaffold protein (ISCU), in coordination with iron and sulfur donor proteins in human mitochondria. Loss of ISCU function leads to myopathy, characterized by muscle wasting and cardiac hypertrophy. In addition to the homozygous ISCU mutation (g.7044G→C), compound heterozygous patients with severe myopathy have been identified to carry the c.149G→A missense mutation converting the glycine 50 residue to glutamate. However, the physiological defects and molecular mechanism associated with G50E mutation have not been elucidated. In this report, we uncover mechanistic insights concerning how the G50E ISCU mutation in humans leads to the development of severe ISCU myopathy, using a human cell line and yeast as the model systems. The biochemical results highlight that the G50E mutation results in compromised interaction with the sulfur donor NFS1 and the J-protein HSCB, thus impairing the rate of Fe-S cluster synthesis. As a result, electron transport chain complexes show significant reduction in their redox properties, leading to loss of cellular respiration. Furthermore, the G50E mutant mitochondria display enhancement in iron level and reactive oxygen species, thereby causing oxidative stress leading to impairment in the mitochondrial functions. Thus, our findings provide compelling evidence that the respiration defect due to impaired biogenesis of Fe-S clusters in myopathy patients leads to manifestation of complex clinical symptoms.
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Affiliation(s)
- Prasenjit Prasad Saha
- Department of Biochemistry, Indian Institute of Science, Biological Sciences Building, Bangalore 560012, Karnataka, India
| | - S K Praveen Kumar
- Department of Biochemistry, Indian Institute of Science, Biological Sciences Building, Bangalore 560012, Karnataka, India
| | - Shubhi Srivastava
- Department of Biochemistry, Indian Institute of Science, Biological Sciences Building, Bangalore 560012, Karnataka, India
| | - Devanjan Sinha
- Department of Biochemistry, Indian Institute of Science, Biological Sciences Building, Bangalore 560012, Karnataka, India
| | - Gautam Pareek
- Department of Biochemistry, Indian Institute of Science, Biological Sciences Building, Bangalore 560012, Karnataka, India
| | - Patrick D'Silva
- Department of Biochemistry, Indian Institute of Science, Biological Sciences Building, Bangalore 560012, Karnataka, India.
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54
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Beilschmidt LK, Puccio HM. Mammalian Fe-S cluster biogenesis and its implication in disease. Biochimie 2014; 100:48-60. [PMID: 24440636 DOI: 10.1016/j.biochi.2014.01.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 01/07/2014] [Indexed: 10/25/2022]
Abstract
Iron-sulfur (Fe-S) clusters are inorganic cofactors that are ubiquitous and essential. Due to their chemical versatility, Fe-S clusters are implicated in a wide range of protein functions including mitochondrial respiration and DNA repair. Composed of iron and sulfur, they are sensible to oxygen and their biogenesis requires a highly conserved protein machinery that facilitates assembly of the cluster as well as its insertion into apoproteins. Mitochondria are the central cellular compartment for Fe-S cluster biogenesis in eukaryotic cells and the importance of proper function of this biogenesis for life is highlighted by a constantly increasing number of human genetic diseases that are associated with dysfunction of this Fe-S cluster biogenesis pathway. Although these disorders are rare and appear dissimilar, common aspects are found among them. This review will give an overview on what is known on mammalian Fe-S cluster biogenesis today, by putting it into the context of what is known from studies from lower model organisms, and focuses on the associated diseases, by drawing attention to the respective mutations. Finally, it outlines the importance of adequate cellular and murine models to uncover not only each protein function, but to resolve their role and requirement throughout the mammalian organism.
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Affiliation(s)
- Lena K Beilschmidt
- Translational Medicine and Neurogenetics, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France; Inserm, U596, Illkirch, France; CNRS, UMR7104, Illkirch, France; Université de Strasbourg, Strasbourg, France; Collège de France, Chaire de génétique humaine, Illkirch, France
| | - Hélène M Puccio
- Translational Medicine and Neurogenetics, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France; Inserm, U596, Illkirch, France; CNRS, UMR7104, Illkirch, France; Université de Strasbourg, Strasbourg, France; Collège de France, Chaire de génétique humaine, Illkirch, France.
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55
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Sequence and domain conservation of the coelacanth Hsp40 and Hsp90 chaperones suggests conservation of function. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 322:359-78. [DOI: 10.1002/jez.b.22541] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 07/13/2013] [Accepted: 08/16/2013] [Indexed: 01/17/2023]
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56
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Ni M, Feretzaki M, Li W, Floyd-Averette A, Mieczkowski P, Dietrich FS, Heitman J. Unisexual and heterosexual meiotic reproduction generate aneuploidy and phenotypic diversity de novo in the yeast Cryptococcus neoformans. PLoS Biol 2013; 11:e1001653. [PMID: 24058295 PMCID: PMC3769227 DOI: 10.1371/journal.pbio.1001653] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 08/01/2013] [Indexed: 01/24/2023] Open
Abstract
Aneuploidy is known to be deleterious and underlies several common human diseases, including cancer and genetic disorders such as trisomy 21 in Down's syndrome. In contrast, aneuploidy can also be advantageous and in fungi confers antifungal drug resistance and enables rapid adaptive evolution. We report here that sexual reproduction generates phenotypic and genotypic diversity in the human pathogenic yeast Cryptococcus neoformans, which is globally distributed and commonly infects individuals with compromised immunity, such as HIV/AIDS patients, causing life-threatening meningoencephalitis. C. neoformans has a defined a-α opposite sexual cycle; however, >99% of isolates are of the α mating type. Interestingly, α cells can undergo α-α unisexual reproduction, even involving genotypically identical cells. A central question is: Why would cells mate with themselves given that sex is costly and typically serves to admix preexisting genetic diversity from genetically divergent parents? In this study, we demonstrate that α-α unisexual reproduction frequently generates phenotypic diversity, and the majority of these variant progeny are aneuploid. Aneuploidy is responsible for the observed phenotypic changes, as chromosome loss restoring euploidy results in a wild-type phenotype. Other genetic changes, including diploidization, chromosome length polymorphisms, SNPs, and indels, were also generated. Phenotypic/genotypic changes were not observed following asexual mitotic reproduction. Aneuploidy was also detected in progeny from a-α opposite-sex congenic mating; thus, both homothallic and heterothallic sexual reproduction can generate phenotypic diversity de novo. Our study suggests that the ability to undergo unisexual reproduction may be an evolutionary strategy for eukaryotic microbial pathogens, enabling de novo genotypic and phenotypic plasticity and facilitating rapid adaptation to novel environments.
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Affiliation(s)
- Min Ni
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Marianna Feretzaki
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Wenjun Li
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Anna Floyd-Averette
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Piotr Mieczkowski
- Department of Genetics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Fred S. Dietrich
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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57
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Stehling O, Lill R. The role of mitochondria in cellular iron-sulfur protein biogenesis: mechanisms, connected processes, and diseases. Cold Spring Harb Perspect Biol 2013; 5:a011312. [PMID: 23906713 DOI: 10.1101/cshperspect.a011312] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Iron-sulfur (Fe/S) clusters belong to the most ancient protein cofactors in life, and fulfill functions in electron transport, enzyme catalysis, homeostatic regulation, and sulfur activation. The synthesis of Fe/S clusters and their insertion into apoproteins requires almost 30 proteins in the mitochondria and cytosol of eukaryotic cells. This review summarizes our current biochemical knowledge of mitochondrial Fe/S protein maturation. Because this pathway is essential for various extramitochondrial processes, we then explain how mitochondria contribute to the mechanism of cytosolic and nuclear Fe/S protein biogenesis, and to other connected processes including nuclear DNA replication and repair, telomere maintenance, and transcription. We next describe how the efficiency of mitochondria to assemble Fe/S proteins is used to regulate cellular iron homeostasis. Finally, we briefly summarize a number of mitochondrial "Fe/S diseases" in which various biogenesis components are functionally impaired owing to genetic mutations. The thorough understanding of the diverse biochemical disease phenotypes helps with testing the current working model for the molecular mechanism of Fe/S protein biogenesis and its connected processes.
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Affiliation(s)
- Oliver Stehling
- Institut für Zytobiologie, Philipps-Universität Marburg, 35032 Marburg, Germany
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58
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Marelja Z, Mullick Chowdhury M, Dosche C, Hille C, Baumann O, Löhmannsröben HG, Leimkühler S. The L-cysteine desulfurase NFS1 is localized in the cytosol where it provides the sulfur for molybdenum cofactor biosynthesis in humans. PLoS One 2013; 8:e60869. [PMID: 23593335 PMCID: PMC3625234 DOI: 10.1371/journal.pone.0060869] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 03/04/2013] [Indexed: 11/18/2022] Open
Abstract
In humans, the L-cysteine desulfurase NFS1 plays a crucial role in the mitochondrial iron-sulfur cluster biosynthesis and in the thiomodification of mitochondrial and cytosolic tRNAs. We have previously demonstrated that purified NFS1 is able to transfer sulfur to the C-terminal domain of MOCS3, a cytosolic protein involved in molybdenum cofactor biosynthesis and tRNA thiolation. However, no direct evidence existed so far for the interaction of NFS1 and MOCS3 in the cytosol of human cells. Here, we present direct data to show the interaction of NFS1 and MOCS3 in the cytosol of human cells using Förster resonance energy transfer and a split-EGFP system. The colocalization of NFS1 and MOCS3 in the cytosol was confirmed by immunodetection of fractionated cells and localization studies using confocal fluorescence microscopy. Purified NFS1 was used to reconstitute the lacking molybdoenzyme activity of the Neurospora crassa nit-1 mutant, giving additional evidence that NFS1 is the sulfur donor for Moco biosynthesis in eukaryotes in general.
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Affiliation(s)
- Zvonimir Marelja
- Department of Molecular Enzymology, Institute of Biochemistry, University of Potsdam, Potsdam, Germany
| | - Mita Mullick Chowdhury
- Department of Molecular Enzymology, Institute of Biochemistry, University of Potsdam, Potsdam, Germany
| | - Carsten Dosche
- Department of Physical Chemistry, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Carsten Hille
- Department of Physical Chemistry, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Otto Baumann
- Department of Animal Physiology, Institute of Biochemistry, University of Potsdam, Potsdam, Germany
| | - Hans-Gerd Löhmannsröben
- Department of Physical Chemistry, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Silke Leimkühler
- Department of Molecular Enzymology, Institute of Biochemistry, University of Potsdam, Potsdam, Germany
- * E-mail:
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59
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Uhrigshardt H, Rouault TA, Missirlis F. Insertion mutants in Drosophila melanogaster Hsc20 halt larval growth and lead to reduced iron-sulfur cluster enzyme activities and impaired iron homeostasis. J Biol Inorg Chem 2013; 18:441-9. [PMID: 23444034 PMCID: PMC3612401 DOI: 10.1007/s00775-013-0988-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 02/07/2013] [Indexed: 10/31/2022]
Abstract
Despite the prominence of iron-sulfur cluster (ISC) proteins in bioenergetics, intermediary metabolism, and redox regulation of cellular, mitochondrial, and nuclear processes, these proteins have been given scarce attention in Drosophila. Moreover, biosynthesis and delivery of ISCs to target proteins requires a highly regulated molecular network that spans different cellular compartments. The only Drosophila ISC biosynthetic protein studied to date is frataxin, in attempts to model Friedreich's ataxia, a disease arising from reduced expression of the human frataxin homologue. One of several proteins involved in ISC biogenesis is heat shock protein cognate 20 (Hsc20). Here we characterize two piggyBac insertion mutants in Drosophila Hsc20 that display larval growth arrest and deficiencies in aconitase and succinate dehydrogenase activities, but not in isocitrate dehydrogenase activity; phenotypes also observed with ubiquitous frataxin RNA interference. Furthermore, a disruption of iron homeostasis in the mutant flies was evidenced by an apparent reduction in induction of intestinal ferritin with ferric iron accumulating in a subcellular pattern reminiscent of mitochondria. These phenotypes were specific to intestinal cell types that regulate ferritin expression, but were notably absent in the iron cells where ferritin is constitutively expressed and apparently translated independently of iron regulatory protein 1A. Hsc20 mutant flies represent an independent tool to disrupt ISC biogenesis in vivo without using the RNA interference machinery.
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Affiliation(s)
- Helge Uhrigshardt
- Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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60
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Crooks DR, Jeong SY, Tong WH, Ghosh MC, Olivierre H, Haller RG, Rouault TA. Tissue specificity of a human mitochondrial disease: differentiation-enhanced mis-splicing of the Fe-S scaffold gene ISCU renders patient cells more sensitive to oxidative stress in ISCU myopathy. J Biol Chem 2012; 287:40119-30. [PMID: 23035118 DOI: 10.1074/jbc.m112.418889] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND ISCU myopathy is a disease caused by muscle-specific deficiency of the Fe-S cluster scaffold protein ISCU. RESULTS MyoD expression enhanced ISCU mRNA mis-splicing, and oxidative stress exacerbated ISCU depletion in patient cells. CONCLUSION ISCU protein deficiency in patients results from muscle-specific mis-splicing as well as oxidative stress. SIGNIFICANCE Oxidative stress negatively influences the mammalian Fe-S cluster assembly machinery by destabilization of ISCU. Iron-sulfur (Fe-S) cluster cofactors are formed on the scaffold protein ISCU. ISCU myopathy is a disease caused by an intronic mutation that leads to abnormally spliced ISCU mRNA. We found that two predominant mis-spliced ISCU mRNAs produce a truncated and short-lived ISCU protein product in multiple patient cell types. Expression of the muscle-specific transcription factor MyoD further diminished normal splicing of ISCU mRNA in patient myoblasts, demonstrating that the process of muscle differentiation enhances the loss of normal ISCU mRNA splicing. ISCU protein was nearly undetectable in patient skeletal muscle, but was higher in patient myoblasts, fibroblasts, and lymphoblasts. We next treated patient cells with pro-oxidants to mimic the oxidative stress associated with muscle activity. Brief hydrogen peroxide treatment or incubation in an enriched oxygen atmosphere led to a marked further reduction of ISCU protein levels, which could be prevented by pretreatment with the antioxidant ascorbate. Thus, we conclude that skeletal muscle differentiation of patient cells causes a higher degree of abnormal ISCU splicing and that oxidative stress resulting from skeletal muscle work destabilizes the small amounts of normal ISCU protein generated in patient skeletal muscles.
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Affiliation(s)
- Daniel R Crooks
- Department of Biochemistry, Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC 20057, USA
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61
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Shakamuri P, Zhang B, Johnson MK. Monothiol glutaredoxins function in storing and transporting [Fe2S2] clusters assembled on IscU scaffold proteins. J Am Chem Soc 2012; 134:15213-6. [PMID: 22963613 PMCID: PMC3446642 DOI: 10.1021/ja306061x] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Indexed: 11/29/2022]
Abstract
In the bacterial ISC system for iron-sulfur cluster assembly, IscU acts as a primary scaffold protein, and the molecular co-chaperones HscA and HscB specifically interact with IscU to facilitate ATP-driven cluster transfer. In this work, cluster transfer from Azotobacter vinelandii [Fe(2)S(2)](2+) cluster-bound IscU to apo-Grx5, a general purpose monothiol glutaredoxin in A. vinelandii, was monitored by circular dichroism spectroscopy, in the absence and in the presence of HscA/HscB/Mg-ATP. The results indicate a 700-fold enhancement in the rate of [Fe(2)S(2)](2+) cluster transfer in the presence of the co-chaperones and Mg-ATP, yielding a second-order rate constant of 20 000 M(-1) min(-1) at 23 °C. Thus, HscA and HscB are required for efficient ATP-dependent [Fe(2)S(2)](2+) cluster transfer from IscU to Grx5. The results support a role for monothiol Grx's in storing and transporting [Fe(2)S(2)](2+) clusters assembled on IscU and illustrate the limitations of interpreting in vitro cluster transfer studies involving [Fe(2)S(2)]-IscU in the absence of the dedicated HscA/HscB co-chaperone system.
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Affiliation(s)
| | | | - Michael K. Johnson
- Department
of Chemistry and Center for Metalloenzyme
Studies, University of Georgia, Athens,
Georgia 30602, United States
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62
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Lill R, Hoffmann B, Molik S, Pierik AJ, Rietzschel N, Stehling O, Uzarska MA, Webert H, Wilbrecht C, Mühlenhoff U. The role of mitochondria in cellular iron-sulfur protein biogenesis and iron metabolism. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1823:1491-508. [PMID: 22609301 DOI: 10.1016/j.bbamcr.2012.05.009] [Citation(s) in RCA: 364] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 05/07/2012] [Accepted: 05/09/2012] [Indexed: 12/21/2022]
Abstract
Mitochondria play a key role in iron metabolism in that they synthesize heme, assemble iron-sulfur (Fe/S) proteins, and participate in cellular iron regulation. Here, we review the latter two topics and their intimate connection. The mitochondrial Fe/S cluster (ISC) assembly machinery consists of 17 proteins that operate in three major steps of the maturation process. First, the cysteine desulfurase complex Nfs1-Isd11 as the sulfur donor cooperates with ferredoxin-ferredoxin reductase acting as an electron transfer chain, and frataxin to synthesize an [2Fe-2S] cluster on the scaffold protein Isu1. Second, the cluster is released from Isu1 and transferred toward apoproteins with the help of a dedicated Hsp70 chaperone system and the glutaredoxin Grx5. Finally, various specialized ISC components assist in the generation of [4Fe-4S] clusters and cluster insertion into specific target apoproteins. Functional defects of the core ISC assembly machinery are signaled to cytosolic or nuclear iron regulatory systems resulting in increased cellular iron acquisition and mitochondrial iron accumulation. In fungi, regulation is achieved by iron-responsive transcription factors controlling the expression of genes involved in iron uptake and intracellular distribution. They are assisted by cytosolic multidomain glutaredoxins which use a bound Fe/S cluster as iron sensor and additionally perform an essential role in intracellular iron delivery to target metalloproteins. In mammalian cells, the iron regulatory proteins IRP1, an Fe/S protein, and IRP2 act in a post-transcriptional fashion to adjust the cellular needs for iron. Thus, Fe/S protein biogenesis and cellular iron metabolism are tightly linked to coordinate iron supply and utilization. This article is part of a Special Issue entitled: Cell Biology of Metals.
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Affiliation(s)
- Roland Lill
- Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Robert-Koch Str. 6, 35033 Marburg, Germany.
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63
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Hoefs SJ, Rodenburg RJ, Smeitink JA, van den Heuvel LP. Molecular base of biochemical complex I deficiency. Mitochondrion 2012; 12:520-32. [DOI: 10.1016/j.mito.2012.07.106] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 07/06/2012] [Accepted: 07/10/2012] [Indexed: 12/21/2022]
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64
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Rouault TA. Biogenesis of iron-sulfur clusters in mammalian cells: new insights and relevance to human disease. Dis Model Mech 2012; 5:155-64. [PMID: 22382365 PMCID: PMC3291637 DOI: 10.1242/dmm.009019] [Citation(s) in RCA: 247] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Iron-sulfur (Fe-S) clusters are ubiquitous cofactors composed of iron and inorganic sulfur. They are required for the function of proteins involved in a wide range of activities, including electron transport in respiratory chain complexes, regulatory sensing, photosynthesis and DNA repair. The proteins involved in the biogenesis of Fe-S clusters are evolutionarily conserved from bacteria to humans, and many insights into the process of Fe-S cluster biogenesis have come from studies of model organisms, including bacteria, fungi and plants. It is now clear that several rare and seemingly dissimilar human diseases are attributable to defects in the basic process of Fe-S cluster biogenesis. Although these diseases –which include Friedreich’s ataxia (FRDA), ISCU myopathy, a rare form of sideroblastic anemia, an encephalomyopathy caused by dysfunction of respiratory chain complex I and multiple mitochondrial dysfunctions syndrome – affect different tissues, a feature common to many of them is that mitochondrial iron overload develops as a secondary consequence of a defect in Fe-S cluster biogenesis. This Commentary outlines the basic steps of Fe-S cluster biogenesis as they have been defined in model organisms. In addition, it draws attention to refinements of the process that might be specific to the subcellular compartmentalization of Fe-S cluster biogenesis proteins in some eukaryotes, including mammals. Finally, it outlines several important unresolved questions in the field that, once addressed, should offer important clues into how mitochondrial iron homeostasis is regulated, and how dysfunction in Fe-S cluster biogenesis can contribute to disease.
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Affiliation(s)
- Tracey A Rouault
- National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.
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65
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Anderson CP, Shen M, Eisenstein RS, Leibold EA. Mammalian iron metabolism and its control by iron regulatory proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1468-83. [PMID: 22610083 DOI: 10.1016/j.bbamcr.2012.05.010] [Citation(s) in RCA: 346] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 05/07/2012] [Accepted: 05/11/2012] [Indexed: 02/06/2023]
Abstract
Cellular iron homeostasis is maintained by iron regulatory proteins 1 and 2 (IRP1 and IRP2). IRPs bind to iron-responsive elements (IREs) located in the untranslated regions of mRNAs encoding protein involved in iron uptake, storage, utilization and export. Over the past decade, significant progress has been made in understanding how IRPs are regulated by iron-dependent and iron-independent mechanisms and the pathological consequences of IRP2 deficiency in mice. The identification of novel IREs involved in diverse cellular pathways has revealed that the IRP-IRE network extends to processes other than iron homeostasis. A mechanistic understanding of IRP regulation will likely yield important insights into the basis of disorders of iron metabolism. This article is part of a Special Issue entitled: Cell Biology of Metals.
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Affiliation(s)
- Cole P Anderson
- Department of Oncological Sciences, University of Utah, 15 N. 2030 E., Salt Lake City, UT 84112, USA
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66
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Mitochondrial chaperone DnaJA3 induces Drp1-dependent mitochondrial fragmentation. Int J Biochem Cell Biol 2012; 44:1366-76. [PMID: 22595283 DOI: 10.1016/j.biocel.2012.05.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2012] [Revised: 04/12/2012] [Accepted: 05/07/2012] [Indexed: 12/14/2022]
Abstract
Mitochondrial morphology is dynamic and controlled by coordinated fusion and fission pathways. The role of mitochondrial chaperones in mitochondrial morphological changes and pathology is currently unclear. Here we report that altered levels of DnaJA3 (Tid1/mtHsp40) a mitochondrial member of the DnaJ protein family, and heat shock protein (Hsp) co-chaperone of matrix 70 kDa Hsp70 (mtHsp70/mortalin/HSPA9), induces mitochondrial fragmentation. Suppression of DnaJA3 induced mitochondrial fragmentation in HeLa cells. Elevated levels of DnaJA3 in normal Hs68 fibroblast cells and HeLa, SKN-SH, U87 and U251 cancer cell lines induces mitochondrial fragmentation. Mitochondrial fragmentation induction was not observed in HeLa cells when other DnaJA family members, or mitochondrial DnaJ protein HSC20, were ectopically expressed, indicating that the effects on mitochondrial morphology were specific to DnaJA3. We show that the DnaJ domain (amino acids 88-168) of DnaJA3 is sufficient for the induction of mitochondrial fragmentation. Furthermore, an H121Q point mutation of the DnaJ domain, which abrogates interaction and activation of mtHsp70 ATPase, eliminates fragmentation induced by DnaJA3. This suggests that DnaJA3 interaction with mtHsp70 may be critical in mitochondrial morphological changes. DnaJA3-induced mitochondrial fragmentation was dependent on fission factor dynamin-related protein 1 (Drp1). Ectopic expression of the mitofusins (Mfn1 and Mfn2), however, does not rescue DnaJA3-induced mitochondrial fragmentation. Lastly, elevated levels of DnaJA3 inducing mitochondrial fragmentation were associated with reduction in cell viability. Taken together, elevated DnaJA3 induces Drp1-depedendent mitochondrial fragmentation and decreased cell viability.
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Sheftel AD, Wilbrecht C, Stehling O, Niggemeyer B, Elsässer HP, Mühlenhoff U, Lill R. The human mitochondrial ISCA1, ISCA2, and IBA57 proteins are required for [4Fe-4S] protein maturation. Mol Biol Cell 2012; 23:1157-66. [PMID: 22323289 PMCID: PMC3315811 DOI: 10.1091/mbc.e11-09-0772] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The human mitochondrial proteins ISCA1, ISCA2, and IBA57 are essential for the generation of mitochondrial [4Fe-4S] proteins in a late step of Fe/S protein biogenesis. This process is important for mitochondrial physiology, as documented by drastic enlargement of the organelles and the loss of cristae membranes in the absence of these proteins. Members of the bacterial and mitochondrial iron–sulfur cluster (ISC) assembly machinery include the so-called A-type ISC proteins, which support the assembly of a subset of Fe/S apoproteins. The human genome encodes two A-type proteins, termed ISCA1 and ISCA2, which are related to Saccharomyces cerevisiae Isa1 and Isa2, respectively. An additional protein, Iba57, physically interacts with Isa1 and Isa2 in yeast. To test the cellular role of human ISCA1, ISCA2, and IBA57, HeLa cells were depleted for any of these proteins by RNA interference technology. Depleted cells contained massively swollen and enlarged mitochondria that were virtually devoid of cristae membranes, demonstrating the importance of these proteins for mitochondrial biogenesis. The activities of mitochondrial [4Fe-4S] proteins, including aconitase, respiratory complex I, and lipoic acid synthase, were diminished following depletion of the three proteins. In contrast, the mitochondrial [2Fe-2S] enzyme ferrochelatase and cellular heme content were unaffected. We further provide evidence against a localization and direct Fe/S protein maturation function of ISCA1 and ISCA2 in the cytosol. Taken together, our data suggest that ISCA1, ISCA2, and IBA57 are specifically involved in the maturation of mitochondrial [4Fe-4S] proteins functioning late in the ISC assembly pathway.
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Affiliation(s)
- Alex D Sheftel
- Institut für Zytobiologie, Philipps-Universität-Marburg, Marburg, Germany
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Bridwell-Rabb J, Winn AM, Barondeau DP. Structure-function analysis of Friedreich's ataxia mutants reveals determinants of frataxin binding and activation of the Fe-S assembly complex. Biochemistry 2011; 50:7265-74. [PMID: 21776984 PMCID: PMC3340929 DOI: 10.1021/bi200895k] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Friedreich's ataxia (FRDA) is a progressive neurodegenerative disease associated with the loss of function of the protein frataxin (FXN) that results from low FXN levels due to a GAA triplet repeat expansion or, occasionally, from missense mutations in the FXN gene. Here biochemical and structural properties of FXN variants, including three FRDA missense mutations (N146K, Q148R, and R165C) and three related mutants (N146A, Q148G, and Q153A), were determined in an effort to understand the structural basis for the loss of function. In vitro assays revealed that although the three FRDA missense mutations exhibited similar losses of cysteine desulfurase and Fe-S cluster assembly activities, the causes for these activation defects were distinct. The R165C variant exhibited a k(cat)/K(M) higher than that of native FXN but weak binding to the NFS1, ISD11, and ISCU2 (SDU) complex, whereas the Q148R variant exhibited the lowest k(cat)/K(M) of the six tested FXN variants and only a modest binding deficiency. The order of the FXN binding affinities for the SDU Fe-S assembly complex was as follows: FXN > Q148R > N146A > Q148G > N146K > Q153A > R165C. Four different classes of FXN variants were identified on the basis of their biochemical properties. Together, these structure-function studies reveal determinants for the binding and allosteric activation of the Fe-S assembly complex and provide insight into how FRDA missense mutations are functionally compromised.
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Affiliation(s)
- Jennifer Bridwell-Rabb
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Andrew M. Winn
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - David P. Barondeau
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
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Tsai CL, Bridwell-Rabb J, Barondeau DP. Friedreich's ataxia variants I154F and W155R diminish frataxin-based activation of the iron-sulfur cluster assembly complex. Biochemistry 2011; 50:6478-87. [PMID: 21671584 PMCID: PMC3319458 DOI: 10.1021/bi200666h] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Friedreich's ataxia (FRDA) is a progressive neurodegenerative disease that has been linked to defects in the protein frataxin (Fxn). Most FRDA patients have a GAA expansion in the first intron of their Fxn gene that decreases protein expression. Some FRDA patients have a GAA expansion on one allele and a missense mutation on the other allele. Few functional details are known for the ∼15 different missense mutations identified in FRDA patients. Here in vitro evidence is presented that indicates the FRDA I154F and W155R variants bind more weakly to the complex of Nfs1, Isd11, and Isu2 and thereby are defective in forming the four-component SDUF complex that constitutes the core of the Fe-S cluster assembly machine. The binding affinities follow the trend Fxn ∼ I154F > W155F > W155A ∼ W155R. The Fxn variants also have diminished ability to function as part of the SDUF complex to stimulate the cysteine desulfurase reaction and facilitate Fe-S cluster assembly. Four crystal structures, including the first for a FRDA variant, reveal specific rearrangements associated with the loss of function and lead to a model for Fxn-based activation of the Fe-S cluster assembly complex. Importantly, the weaker binding and lower activity for FRDA variants correlate with the severity of disease progression. Together, these results suggest that Fxn facilitates sulfur transfer from Nfs1 to Isu2 and that these in vitro assays are sensitive and appropriate for deciphering functional defects and mechanistic details for human Fe-S cluster biosynthesis.
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