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Patra S, Barondeau DP. Mechanism of activation of the human cysteine desulfurase complex by frataxin. Proc Natl Acad Sci U S A 2019; 116:19421-19430. [PMID: 31511419 PMCID: PMC6765240 DOI: 10.1073/pnas.1909535116] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The function of frataxin (FXN) has garnered great scientific interest since its depletion was linked to the incurable neurodegenerative disease Friedreich's ataxia (FRDA). FXN has been shown to be necessary for iron-sulfur (Fe-S) cluster biosynthesis and proper mitochondrial function. The structural and functional core of the Fe-S cluster assembly complex is a low-activity pyridoxal 5'-phosphate (PLP)-dependent cysteine desulfurase enzyme that consists of catalytic (NFS1), LYRM protein (ISD11), and acyl carrier protein (ACP) subunits. Although previous studies show that FXN stimulates the activity of this assembly complex, the mechanism of FXN activation is poorly understood. Here, we develop a radiolabeling assay and use stopped-flow kinetics to establish that FXN is functionally linked to the mobile S-transfer loop cysteine of NFS1. Our results support key roles for this essential cysteine residue in substrate binding, as a general acid to advance the Cys-quinonoid PLP intermediate, as a nucleophile to form an NFS1 persulfide, and as a sulfur delivery agent to generate a persulfide species on the Fe-S scaffold protein ISCU2. FXN specifically accelerates each of these individual steps in the mechanism. Our resulting architectural switch model explains why the human Fe-S assembly system has low inherent activity and requires activation, the connection between the functional mobile S-transfer loop cysteine and FXN binding, and why the prokaryotic system does not require a similar FXN-based activation. Together, these results provide mechanistic insights into the allosteric-activator role of FXN and suggest new strategies to replace FXN function in the treatment of FRDA.
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Affiliation(s)
- Shachin Patra
- Department of Chemistry, Texas A&M University, College Station, TX 77842
| | - David P Barondeau
- Department of Chemistry, Texas A&M University, College Station, TX 77842
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2
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Ferreira GC, Oberstaller J, Fonseca R, Keller TE, Adapa SR, Gibbons J, Wang C, Liu X, Li C, Pham M, Dayhoff Ii GW, Duong LM, Reyes LT, Laratelli LE, Franz D, Fatumo S, Bari AG, Freischel A, Fiedler L, Dokur O, Sharma K, Cragun D, Busby B, Jiang RHY. Iron Hack - A symposium/hackathon focused on porphyrias, Friedreich's ataxia, and other rare iron-related diseases. F1000Res 2019; 8:1135. [PMID: 31824661 PMCID: PMC6894363 DOI: 10.12688/f1000research.19140.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/05/2019] [Indexed: 01/14/2023] Open
Abstract
Background: Basic and clinical scientific research at the University of South Florida (USF) have intersected to support a multi-faceted approach around a common focus on rare iron-related diseases. We proposed a modified version of the National Center for Biotechnology Information’s (NCBI) Hackathon-model to take full advantage of local expertise in building “Iron Hack”, a rare disease-focused hackathon. As the collaborative, problem-solving nature of hackathons tends to attract participants of highly-diverse backgrounds, organizers facilitated a symposium on rare iron-related diseases, specifically porphyrias and Friedreich’s ataxia, pitched at general audiences. Methods: The hackathon was structured to begin each day with presentations by expert clinicians, genetic counselors, researchers focused on molecular and cellular biology, public health/global health, genetics/genomics, computational biology, bioinformatics, biomolecular science, bioengineering, and computer science, as well as guest speakers from the American Porphyria Foundation (APF) and Friedreich’s Ataxia Research Alliance (FARA) to inform participants as to the human impact of these diseases. Results: As a result of this hackathon, we developed resources that are relevant not only to these specific disease-models, but also to other rare diseases and general bioinformatics problems. Within two and a half days, “Iron Hack” participants successfully built collaborative projects to visualize data, build databases, improve rare disease diagnosis, and study rare-disease inheritance. Conclusions: The purpose of this manuscript is to demonstrate the utility of a hackathon model to generate prototypes of generalizable tools for a given disease and train clinicians and data scientists to interact more effectively.
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Affiliation(s)
- Gloria C Ferreira
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, MDC 7, Tampa, FL, 33612, USA
| | - Jenna Oberstaller
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Renée Fonseca
- Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa, FL, 33612, USA
| | - Thomas E Keller
- University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Swamy Rakesh Adapa
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Justin Gibbons
- Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa, FL, 33612, USA
| | - Chengqi Wang
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Xiaoming Liu
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Chang Li
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Minh Pham
- Center for Urban Transportation Research, University of South Florida, 4202 E. Fowler Avenue, CUT100, Tampa, FL, 33620, USA
| | - Guy W Dayhoff Ii
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE 205, Tampa, FL, 33620-5250, USA
| | - Linh M Duong
- College of Public Health, University of South Florida, 13201 Bruce B. Downs Blvd., MDC 56, Tampa, FL, 33612, USA.,Moffitt Cancer Center, Tampa, FL, 33612, USA
| | - Luis Tañón Reyes
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Ave, ISA 2015 Tampa, FL, 33620, USA
| | - Luciano Enrique Laratelli
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE 205, Tampa, FL, 33620-5250, USA
| | - Douglas Franz
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE 205, Tampa, FL, 33620-5250, USA
| | - Segun Fatumo
- MRC/UVRI and LSHTM (Uganda Research Unit), Entebbe, Uganda
| | - Atm Golam Bari
- Department of Computer Science and Engineering, University of South Florida, Tampa, FL, USA
| | | | - Lindsey Fiedler
- College of Public Health, University of South Florida, 13201 Bruce B. Downs Blvd., MDC 56, Tampa, FL, 33612, USA
| | - Omkar Dokur
- Department of Computer Science and Engineering, University of South Florida, Tampa, FL, USA
| | | | - Deborah Cragun
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Ben Busby
- National Library of Medicine, 8600 Rockville Pike, Bethesda, MD, 20894-6075, USA
| | - Rays H Y Jiang
- Global and Planetary Health, College of Public Health, University of South Florida, USF Genomics Program, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
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3
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Télot L, Rousseau E, Lesuisse E, Garcia C, Morlet B, Léger T, Camadro JM, Serre V. Quantitative proteomics in Friedreich's ataxia B-lymphocytes: A valuable approach to decipher the biochemical events responsible for pathogenesis. Biochim Biophys Acta Mol Basis Dis 2018; 1864:997-1009. [DOI: 10.1016/j.bbadis.2018.01.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 12/19/2017] [Accepted: 01/08/2018] [Indexed: 11/29/2022]
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Ahlgren EC, Fekry M, Wiemann M, Söderberg CA, Bernfur K, Gakh O, Rasmussen M, Højrup P, Emanuelsson C, Isaya G, Al-Karadaghi S. Iron-induced oligomerization of human FXN81-210 and bacterial CyaY frataxin and the effect of iron chelators. PLoS One 2017; 12:e0188937. [PMID: 29200434 PMCID: PMC5714350 DOI: 10.1371/journal.pone.0188937] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 11/15/2017] [Indexed: 12/12/2022] Open
Abstract
Patients suffering from the progressive neurodegenerative disease Friedreich's ataxia have reduced expression levels of the protein frataxin. Three major isoforms of human frataxin have been identified, FXN42-210, FXN56-210 and FXN81-210, of which FXN81-210 is considered to be the mature form. Both long forms, FXN42-210 and FXN56-210, have been shown to spontaneously form oligomeric particles stabilized by the extended N-terminal sequence. The short variant FXN81-210, on other hand, has only been observed in the monomeric state. However, a highly homologous E. coli frataxin CyaY, which also lacks an N-terminal extension, has been shown to oligomerize in the presence of iron. To explore the mechanisms of stabilization of short variant frataxin oligomers we compare here the effect of iron on the oligomerization of CyaY and FXN81-210. Using dynamic light scattering, small-angle X-ray scattering, electron microscopy (EM) and cross linking mass spectrometry (MS), we show that at aerobic conditions in the presence of iron both FXN81-210 and CyaY form oligomers. However, while CyaY oligomers are stable over time, FXN81-210 oligomers are unstable and dissociate into monomers after about 24 h. EM and MS studies suggest that within the oligomers FXN81-210 and CyaY monomers are packed in a head-to-tail fashion in ring-shaped structures with potential iron-binding sites located at the interface between monomers. The higher stability of CyaY oligomers can be explained by a higher number of acidic residues at the interface between monomers, which may result in a more stable iron binding. We also show that CyaY oligomers may be dissociated by ferric iron chelators deferiprone and DFO, as well as by the ferrous iron chelator BIPY. Surprisingly, deferiprone and DFO stimulate FXN81-210 oligomerization, while BIPY does not show any effect on oligomerization in this case. The results suggest that FXN81-210 oligomerization is primarily driven by ferric iron, while both ferric and ferrous iron participate in CyaY oligomer stabilization. Analysis of the amino acid sequences of bacterial and eukaryotic frataxins suggests that variations in the position of the acidic residues in helix 1, β-strand 1 and the loop between them may control the mode of frataxin oligomerization.
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Affiliation(s)
- Eva-Christina Ahlgren
- Center for Molecular Protein Science, Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
| | - Mostafa Fekry
- Center for Molecular Protein Science, Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
- Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt
| | - Mathias Wiemann
- Center for Molecular Protein Science, Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
| | - Christopher A. Söderberg
- Center for Molecular Protein Science, Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
| | - Katja Bernfur
- Center for Molecular Protein Science, Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
| | - Olex Gakh
- Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota, United States of America
| | - Morten Rasmussen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Peter Højrup
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Cecilia Emanuelsson
- Center for Molecular Protein Science, Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
| | - Grazia Isaya
- Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota, United States of America
| | - Salam Al-Karadaghi
- Center for Molecular Protein Science, Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
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5
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SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY. PLoS One 2017; 12:e0184961. [PMID: 28931050 PMCID: PMC5607177 DOI: 10.1371/journal.pone.0184961] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 09/04/2017] [Indexed: 01/19/2023] Open
Abstract
Frataxin is a highly conserved protein found in both prokaryotes and eukaryotes. It is involved in several central functions in cells, which include iron delivery to biochemical processes, such as heme synthesis, assembly of iron-sulfur clusters (ISC), storage of surplus iron in conditions of iron overload, and repair of ISC in aconitase. Frataxin from different organisms has been shown to undergo iron-dependent oligomerization. At least two different classes of oligomers, with different modes of oligomer packing and stabilization, have been identified. Here, we continue our efforts to explore the factors that control the oligomerization of frataxin from different organisms, and focus on E. coli frataxin CyaY. Using small-angle X-ray scattering (SAXS), we show that higher iron-to-protein ratios lead to larger oligomeric species, and that oligomerization proceeds in a linear fashion as a results of iron oxidation. Native mass spectrometry and online size-exclusion chromatography combined with SAXS show that a dimer is the most common form of CyaY in the presence of iron at atmospheric conditions. Modeling of the dimer using the SAXS data confirms the earlier proposed head-to-tail packing arrangement of monomers. This packing mode brings several conserved acidic residues into close proximity to each other, creating an environment for metal ion binding and possibly even mineralization. Together with negative-stain electron microscopy, the experiments also show that trimers, tetramers, pentamers, and presumably higher-order oligomers may exist in solution. Nano-differential scanning fluorimetry shows that the oligomers have limited stability and may easily dissociate at elevated temperatures. The factors affecting the possible oligomerization mode are discussed.
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Galeano BK, Ranatunga W, Gakh O, Smith DY, Thompson JR, Isaya G. Zinc and the iron donor frataxin regulate oligomerization of the scaffold protein to form new Fe-S cluster assembly centers. Metallomics 2017; 9:773-801. [PMID: 28548666 PMCID: PMC5552075 DOI: 10.1039/c7mt00089h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 05/02/2017] [Indexed: 02/06/2023]
Abstract
Early studies of the bacterial Fe-S cluster assembly system provided structural details for how the scaffold protein and the cysteine desulfurase interact. This work and additional work on the yeast and human systems elucidated a conserved mechanism for sulfur donation but did not provide any conclusive insights into the mechanism for iron delivery from the iron donor, frataxin, to the scaffold. We previously showed that oligomerization is a mechanism by which yeast frataxin (Yfh1) can promote assembly of the core machinery for Fe-S cluster synthesis both in vitro and in cells, in such a manner that the scaffold protein, Isu1, can bind to Yfh1 independent of the presence of the cysteine desulfurase, Nfs1. Here, in the absence of Yfh1, Isu1 was found to exist in two forms, one mostly monomeric with limited tendency to dimerize, and one with a strong propensity to oligomerize. Whereas the monomeric form is stabilized by zinc, the loss of zinc promotes formation of dimer and higher order oligomers. However, upon binding to oligomeric Yfh1, both forms take on a similar symmetrical trimeric configuration that places the Fe-S cluster coordinating residues of Isu1 in close proximity of iron-binding residues of Yfh1. This configuration is suitable for docking of Nfs1 in a manner that provides a structural context for coordinate iron and sulfur donation to the scaffold. Moreover, distinct structural features suggest that in physiological conditions the zinc-regulated abundance of monomeric vs. oligomeric Isu1 yields [Yfh1]·[Isu1] complexes with different Isu1 configurations that afford unique functional properties for Fe-S cluster assembly and delivery.
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Affiliation(s)
- B. K. Galeano
- Department of Pediatric & Adolescent Medicine , Mayo Clinic , Rochester , Minnesota , USA . ;
- Department of Biochemistry & Molecular Biology , Mayo Clinic , Rochester , Minnesota , USA
- Mayo Clinic Graduate School of Biomedical Sciences , Rochester , Minnesota , USA
| | - W. Ranatunga
- Department of Pediatric & Adolescent Medicine , Mayo Clinic , Rochester , Minnesota , USA . ;
- Mayo Clinic Children's Research Center , Rochester , Minnesota , USA
| | - O. Gakh
- Department of Pediatric & Adolescent Medicine , Mayo Clinic , Rochester , Minnesota , USA . ;
- Mayo Clinic Children's Research Center , Rochester , Minnesota , USA
| | - D. Y. Smith
- Department of Pediatric & Adolescent Medicine , Mayo Clinic , Rochester , Minnesota , USA . ;
- Mayo Clinic Children's Research Center , Rochester , Minnesota , USA
| | - J. R. Thompson
- Department of Biochemistry & Molecular Biology , Mayo Clinic , Rochester , Minnesota , USA
| | - G. Isaya
- Department of Pediatric & Adolescent Medicine , Mayo Clinic , Rochester , Minnesota , USA . ;
- Department of Biochemistry & Molecular Biology , Mayo Clinic , Rochester , Minnesota , USA
- Mayo Clinic Children's Research Center , Rochester , Minnesota , USA
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Söderberg C, Gillam ME, Ahlgren EC, Hunter GA, Gakh O, Isaya G, Ferreira GC, Al-Karadaghi S. The Structure of the Complex between Yeast Frataxin and Ferrochelatase: CHARACTERIZATION AND PRE-STEADY STATE REACTION OF FERROUS IRON DELIVERY AND HEME SYNTHESIS. J Biol Chem 2016; 291:11887-98. [PMID: 27026703 PMCID: PMC4882455 DOI: 10.1074/jbc.m115.701128] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 03/11/2016] [Indexed: 01/08/2023] Open
Abstract
Frataxin is a mitochondrial iron-binding protein involved in iron storage, detoxification, and delivery for iron sulfur-cluster assembly and heme biosynthesis. The ability of frataxin from different organisms to populate multiple oligomeric states in the presence of metal ions, e.g. Fe(2+) and Co(2+), led to the suggestion that different oligomers contribute to the functions of frataxin. Here we report on the complex between yeast frataxin and ferrochelatase, the terminal enzyme of heme biosynthesis. Protein-protein docking and cross-linking in combination with mass spectroscopic analysis and single-particle reconstruction from negatively stained electron microscopic images were used to verify the Yfh1-ferrochelatase interactions. The model of the complex indicates that at the 2:1 Fe(2+)-to-protein ratio, when Yfh1 populates a trimeric state, there are two interaction interfaces between frataxin and the ferrochelatase dimer. Each interaction site involves one ferrochelatase monomer and one frataxin trimer, with conserved polar and charged amino acids of the two proteins positioned at hydrogen-bonding distances from each other. One of the subunits of the Yfh1 trimer interacts extensively with one subunit of the ferrochelatase dimer, contributing to the stability of the complex, whereas another trimer subunit is positioned for Fe(2+) delivery. Single-turnover stopped-flow kinetics experiments demonstrate that increased rates of heme production result from monomers, dimers, and trimers, indicating that these forms are most efficient in delivering Fe(2+) to ferrochelatase and sustaining porphyrin metalation. Furthermore, they support the proposal that frataxin-mediated delivery of this potentially toxic substrate overcomes formation of reactive oxygen species.
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Affiliation(s)
- Christopher Söderberg
- From the Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00 Lund, Sweden
| | - Mallory E Gillam
- Department of Molecular Medicine, Morsani College of Medicine and
| | - Eva-Christina Ahlgren
- From the Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00 Lund, Sweden
| | - Gregory A Hunter
- Department of Molecular Medicine, Morsani College of Medicine and
| | - Oleksandr Gakh
- the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905
| | - Grazia Isaya
- the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905
| | - Gloria C Ferreira
- Department of Molecular Medicine, Morsani College of Medicine and the Department of Chemistry, University of South Florida, Tampa, Florida 33612, and
| | - Salam Al-Karadaghi
- From the Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00 Lund, Sweden,
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Ranatunga W, Gakh O, Galeano BK, Smith DY, Söderberg CAG, Al-Karadaghi S, Thompson JR, Isaya G. Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery: THE SUB-COMPLEX FORMED BY THE IRON DONOR, Yfh1 PROTEIN, AND THE SCAFFOLD, Isu1 PROTEIN. J Biol Chem 2016; 291:10378-98. [PMID: 26941001 PMCID: PMC4858984 DOI: 10.1074/jbc.m115.712414] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 02/26/2016] [Indexed: 12/18/2022] Open
Abstract
The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24 Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly.
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Affiliation(s)
- Wasantha Ranatunga
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and
| | - Oleksandr Gakh
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and
| | - Belinda K Galeano
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and
| | - Douglas Y Smith
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and
| | - Christopher A G Söderberg
- the Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden
| | - Salam Al-Karadaghi
- the Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden
| | - James R Thompson
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905 and
| | - Grazia Isaya
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and
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Archibald SJ, Atkin SL, Bras W, Diego-Taboada A, Mackenzie G, Mosselmans JFW, Nikitenko S, Quinn PD, Thomas MF, Young NA. How does iron interact with sporopollenin exine capsules? An X-ray absorption study including microfocus XANES and XRF imaging. J Mater Chem B 2014; 2:945-959. [DOI: 10.1039/c3tb21523g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Pastore A, Puccio H. Frataxin: a protein in search for a function. J Neurochem 2013; 126 Suppl 1:43-52. [PMID: 23859340 DOI: 10.1111/jnc.12220] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Revised: 01/18/2013] [Accepted: 01/23/2013] [Indexed: 01/01/2023]
Abstract
Reduced levels of the protein frataxin cause the neurodegenerative disease Friedreich's ataxia. Pathology is associated with disruption of iron-sulfur cluster biosynthesis, mitochondrial iron overload, and oxidative stress. Frataxin is a highly conserved iron-binding protein present in most organisms. Despite the intense interest generated since the determination of its pathology, identification of the cellular function of frataxin has so far remained elusive. In this review, we revisit the most significant milestones that have led us to our current understanding of frataxin and its functions. The picture that emerges is that frataxin is a crucial element of one of the most essential cellular machines specialized in iron-sulfur cluster biogenesis. Future developments, therefore, can be expected from further advancements in our comprehension of this machine.
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11
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Söderberg CAG, Rajan S, Shkumatov AV, Gakh O, Schaefer S, Ahlgren EC, Svergun DI, Isaya G, Al-Karadaghi S. The molecular basis of iron-induced oligomerization of frataxin and the role of the ferroxidation reaction in oligomerization. J Biol Chem 2013; 288:8156-8167. [PMID: 23344952 PMCID: PMC3605634 DOI: 10.1074/jbc.m112.442285] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 01/22/2013] [Indexed: 11/06/2022] Open
Abstract
The role of the mitochondrial protein frataxin in iron storage and detoxification, iron delivery to iron-sulfur cluster biosynthesis, heme biosynthesis, and aconitase repair has been extensively studied during the last decade. However, still no general consensus exists on the details of the mechanism of frataxin function and oligomerization. Here, using small-angle x-ray scattering and x-ray crystallography, we describe the solution structure of the oligomers formed during the iron-dependent assembly of yeast (Yfh1) and Escherichia coli (CyaY) frataxin. At an iron-to-protein ratio of 2, the initially monomeric Yfh1 is converted to a trimeric form in solution. The trimer in turn serves as the assembly unit for higher order oligomers induced at higher iron-to-protein ratios. The x-ray crystallographic structure obtained from iron-soaked crystals demonstrates that iron binds at the trimer-trimer interaction sites, presumably contributing to oligomer stabilization. For the ferroxidation-deficient D79A/D82A variant of Yfh1, iron-dependent oligomerization may still take place, although >50% of the protein is found in the monomeric state at the highest iron-to-protein ratio used. This demonstrates that the ferroxidation reaction controls frataxin assembly and presumably the iron chaperone function of frataxin and its interactions with target proteins. For E. coli CyaY, the assembly unit of higher order oligomers is a tetramer, which could be an effect of the much shorter N-terminal region of this protein. The results show that understanding of the mechanistic features of frataxin function requires detailed knowledge of the interplay between the ferroxidation reaction, iron-induced oligomerization, and the structure of oligomers formed during assembly.
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Affiliation(s)
- Christopher A G Söderberg
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden
| | - Sreekanth Rajan
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden
| | - Alexander V Shkumatov
- European Molecular Biology Laboratory (EMBL), Hamburg Unit c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany
| | - Oleksandr Gakh
- Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905
| | - Susanne Schaefer
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden
| | - Eva-Christina Ahlgren
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden
| | - Dmitri I Svergun
- European Molecular Biology Laboratory (EMBL), Hamburg Unit c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany
| | - Grazia Isaya
- Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905.
| | - Salam Al-Karadaghi
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden.
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12
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Bali S, Bali G, Huggins FE, Seehra MS, Singh V, Hancock JM, Harrison R, Huffman GP, Pugmire RJ, Ernst RD, Eyring EM. Synthetic Doped Amorphous Ferrihydrite for the Fischer–Tropsch Synthesis of Alternative Fuels. Ind Eng Chem Res 2012. [DOI: 10.1021/ie200777v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sumit Bali
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Garima Bali
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Frank E. Huggins
- Consortium for Fossil Fuel Science
and Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky
40506, United States
| | - Mohindar S. Seehra
- Department of Physics, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Vivek Singh
- Department of Physics, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Jared M. Hancock
- Department of Chemistry
and Biochemistry, Brigham Young University, Provo, Utah 84602, United States
| | - Roger Harrison
- Department of Chemistry
and Biochemistry, Brigham Young University, Provo, Utah 84602, United States
| | - Gerald P. Huffman
- Consortium for Fossil Fuel Science
and Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky
40506, United States
| | - Ronald J. Pugmire
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Richard D. Ernst
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Edward M. Eyring
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
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13
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Söderberg CAG, Shkumatov AV, Rajan S, Gakh O, Svergun DI, Isaya G, Al-Karadaghi S. Oligomerization propensity and flexibility of yeast frataxin studied by X-ray crystallography and small-angle X-ray scattering. J Mol Biol 2011; 414:783-97. [PMID: 22051511 PMCID: PMC3332085 DOI: 10.1016/j.jmb.2011.10.034] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 09/29/2011] [Accepted: 10/19/2011] [Indexed: 02/04/2023]
Abstract
Frataxin is a mitochondrial protein with a central role in iron homeostasis. Defects in frataxin function lead to Friedreich's ataxia, a progressive neurodegenerative disease with childhood onset. The function of frataxin has been shown to be closely associated with its ability to form oligomeric species; however, the factors controlling oligomerization and the types of oligomers present in solution are a matter of debate. Using small-angle X-ray scattering, we found that Co(2+), glycerol, and a single amino acid substitution at the N-terminus, Y73A, facilitate oligomerization of yeast frataxin, resulting in a dynamic equilibrium between monomers, dimers, trimers, hexamers, and higher-order oligomers. Using X-ray crystallography, we found that Co(2+) binds inside the channel at the 3-fold axis of the trimer, which suggests that the metal has an oligomer-stabilizing role. The results reveal the types of oligomers present in solution and support our earlier suggestions that the trimer is the main building block of yeast frataxin oligomers. They also indicate that different mechanisms may control oligomer stability and oligomerization in vivo.
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Affiliation(s)
- Christopher AG Söderberg
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, PO Box 124, SE-221 00 Lund, Sweden
| | | | - Sreekanth Rajan
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, PO Box 124, SE-221 00 Lund, Sweden
| | - Oleksandr Gakh
- Department of Pediatric and Adolescent Medicine and Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905
| | | | - Grazia Isaya
- Department of Pediatric and Adolescent Medicine and Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905
| | - Salam Al-Karadaghi
- Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, PO Box 124, SE-221 00 Lund, Sweden
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Abstract
Friedreich's Ataxia is the most common inherited ataxia in man. It is a mitochondrial disease caused by severely reduced expression of the iron binding protein, frataxin. A large GAA triplet expansion in the human FRDA gene encoding this protein inhibits expression of this gene. It is inherited in an autosomal recessive pattern and typically diagnosed in childhood. The primary symptoms include severe and progressive neuropathy, and a hypertrophic cardiomyopathy that may cause death. The cardiomyopathy is difficult to treat and is frequently associated with arrhythmias, heart failure, and intolerance of cardiovascular stress, such as surgeries. Innovative approaches to therapy, such as histone deacetylase inhibitors, and enzyme replacement with cell penetrant peptide fusion proteins, hold promise for this and other similar mitochondrial disorders. This review will focus on the basic findings of this disease, and the cardiomyopathy associated with its diagnosis.
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Affiliation(s)
- R Mark Payne
- Riley Heart Research Center, Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN, 46202
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15
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Haikarainen T, Paturi P, Lindén J, Haataja S, Meyer-Klaucke W, Finne J, Papageorgiou AC. Magnetic properties and structural characterization of iron oxide nanoparticles formed by Streptococcus suis Dpr and four mutants. J Biol Inorg Chem 2011; 16:799-807. [PMID: 21487937 DOI: 10.1007/s00775-011-0781-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 03/30/2011] [Indexed: 01/30/2023]
Abstract
Streptococcus suis Dpr belongs to the Dps family of bacterial and archaeal proteins that oxidize Fe(2+) to Fe(3+) to protect microorganisms from oxidative damage. The oxidized iron is subsequently deposited as ferrihydrite inside a protein cavity, resulting in the formation of an iron core. The size and the magnetic properties of the iron core have attracted considerable attention for nanotechnological applications in recent years. Here, the magnetic and structural properties of the iron core in wild-type Dpr and four cavity mutants were studied. All samples clearly demonstrated a superparamagnetic behavior in superconducting quantum interference device magnetometry and Mössbauer spectroscopy compatible with that of superparamagnetic ferrihydrite nanoparticles. However, all the mutants exhibited higher magnetic moments than the wild-type protein. Furthermore, measurement of the iron content with inductively coupled plasma mass spectrometry revealed a smaller amount of iron in the iron cores of the mutants, suggesting that the mutations affect nucleation and iron deposition inside the cavity. The X-ray crystal structures of the mutants revealed no changes compared with the wild-type crystal structure; thus, the differences in the magnetic moments could not be attributed to structural changes in the protein. Extended X-ray absorption fine structure measurements showed that the coordination geometry of the iron cores of the mutants was similar to that of the wild-type protein. Taken together, these results suggest that mutation of the residues that surround the iron storage cavity could be exploited to selectively modify the magnetic properties of the iron core without affecting the structure of the protein and the geometry of the iron core.
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Affiliation(s)
- Teemu Haikarainen
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku, Finland.
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16
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Santos R, Lefevre S, Sliwa D, Seguin A, Camadro JM, Lesuisse E. Friedreich ataxia: molecular mechanisms, redox considerations, and therapeutic opportunities. Antioxid Redox Signal 2010; 13:651-90. [PMID: 20156111 PMCID: PMC2924788 DOI: 10.1089/ars.2009.3015] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 02/08/2010] [Accepted: 02/14/2010] [Indexed: 12/14/2022]
Abstract
Mitochondrial dysfunction and oxidative damage are at the origin of numerous neurodegenerative diseases like Friedreich ataxia and Alzheimer and Parkinson diseases. Friedreich ataxia (FRDA) is the most common hereditary ataxia, with one individual affected in 50,000. This disease is characterized by progressive degeneration of the central and peripheral nervous systems, cardiomyopathy, and increased incidence of diabetes mellitus. FRDA is caused by a dynamic mutation, a GAA trinucleotide repeat expansion, in the first intron of the FXN gene. Fewer than 5% of the patients are heterozygous and carry point mutations in the other allele. The molecular consequences of the GAA triplet expansion is transcription silencing and reduced expression of the encoded mitochondrial protein, frataxin. The precise cellular role of frataxin is not known; however, it is clear now that several mitochondrial functions are not performed correctly in patient cells. The affected functions include respiration, iron-sulfur cluster assembly, iron homeostasis, and maintenance of the redox status. This review highlights the molecular mechanisms that underlie the disease phenotypes and the different hypothesis about the function of frataxin. In addition, we present an overview of the most recent therapeutic approaches for this severe disease that actually has no efficient treatment.
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Affiliation(s)
- Renata Santos
- Mitochondria, Metals and Oxidative Stress Laboratory, Institut Jacques Monod (UMR 7592 CNRS–University Paris-Diderot), Paris, France
| | - Sophie Lefevre
- Mitochondria, Metals and Oxidative Stress Laboratory, Institut Jacques Monod (UMR 7592 CNRS–University Paris-Diderot), Paris, France
- University Pierre et Marie Curie, Paris, France
| | - Dominika Sliwa
- Mitochondria, Metals and Oxidative Stress Laboratory, Institut Jacques Monod (UMR 7592 CNRS–University Paris-Diderot), Paris, France
| | - Alexandra Seguin
- Mitochondria, Metals and Oxidative Stress Laboratory, Institut Jacques Monod (UMR 7592 CNRS–University Paris-Diderot), Paris, France
| | - Jean-Michel Camadro
- Mitochondria, Metals and Oxidative Stress Laboratory, Institut Jacques Monod (UMR 7592 CNRS–University Paris-Diderot), Paris, France
| | - Emmanuel Lesuisse
- Mitochondria, Metals and Oxidative Stress Laboratory, Institut Jacques Monod (UMR 7592 CNRS–University Paris-Diderot), Paris, France
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17
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Armstrong JS, Khdour O, Hecht SM. Does oxidative stress contribute to the pathology of Friedreich's ataxia? A radical question. FASEB J 2010; 24:2152-63. [PMID: 20219987 DOI: 10.1096/fj.09-143222] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Friedreich's ataxia (FRDA) is a hereditary neurodegenerative disease that frequently culminates in cardiac failure at an early age. FRDA is believed to arise from reduced synthesis of the mitochondrial iron chaperone frataxin due to impaired gene transcription, which leads to mitochondrial iron accumulation, dysfunction of mitochondrial Fe-S containing enzymes, and increased Fenton-mediated free radical production. Recent reports have challenged this generally accepted hypothesis, by suggesting that the oxidative stress component in FRDA is minimal and thereby questioning the benefit of antioxidant therapeutic strategies. We suggest that this apparent paradox results from the radically divergent chemistries of the participating reactive oxygen species (ROS), the major cellular subcompartments involved and the overall cellular responses to ROS. In this review, we consider these factors and conclude that oxidative stress does constitute a major contributing factor to FRDA pathology. This reaffirms the idea that the rational design of specific small molecule multifunctional antioxidants will benefit FRDA patients.
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Affiliation(s)
- Jeffrey S Armstrong
- Center for BioEnergetics, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA.
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18
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Popescu BFG, Nichol H. Mapping brain metals to evaluate therapies for neurodegenerative disease. CNS Neurosci Ther 2010; 17:256-68. [PMID: 20553312 DOI: 10.1111/j.1755-5949.2010.00149.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The brain is rich in metals and has a high metabolic rate, making it acutely vulnerable to the toxic effects of endogenously produced free radicals. The abundant metals, iron and copper, transfer single electrons as they cycle between their reduced (Fe(2+) , Cu(1+) ) and oxidized (Fe(3+) , Cu(2+) ) states making them powerful catalysts of reactive oxygen species (ROS) production. Even redox inert zinc, if present in excess, can trigger ROS production indirectly by altering mitochondrial function. While metal chelators seem to improve the clinical outcome of several neurodegenerative diseases, their mechanisms of action remain obscure and the effects of long-term use are largely unknown. Most chelators are not specific to a single metal and could alter the distribution of multiple metals in the brain, leading to unexpected consequences over the long-term. We show here how X-ray fluorescence will be a valuable tool to examine the effect of chelators on the distribution and amount of metals in the brain.
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Seguin A, Sutak R, Bulteau AL, Garcia-Serres R, Oddou JL, Lefevre S, Santos R, Dancis A, Camadro JM, Latour JM, Lesuisse E. Evidence that yeast frataxin is not an iron storage protein in vivo. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1802:531-8. [PMID: 20307653 DOI: 10.1016/j.bbadis.2010.03.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2009] [Revised: 03/14/2010] [Accepted: 03/16/2010] [Indexed: 11/29/2022]
Abstract
Yeast cells deficient in the yeast frataxin homolog (Yfh1p) accumulate iron in their mitochondria. Whether this iron is toxic, however, remains unclear. We showed that large excesses of iron in the growth medium did not inhibit growth and did not decrease cell viability. Increasing the ratio of mitochondrial iron-to-Yfh1p by decreasing the steady-state level of Yfh1p to less than 100 molecules per cell had very few deleterious effects on cell physiology, even though the mitochondrial iron concentration greatly exceeded the iron-binding capacity of Yfh1p in these conditions. Mössbauer spectroscopy and FPLC analyses of whole mitochondria or of isolated mitochondrial matrices showed that the chemical and biochemical forms of the accumulated iron in mitochondria of mutant yeast strains (Deltayfh1, Deltaggc1 and Deltassq1) displayed a nearly identical distribution. This was also the case for Deltaggc1 cells, in which Yfh1p was overproduced. In these mitochondria, most of the iron was insoluble, and the ratio of soluble-to-insoluble iron did not change when the amount of Yfh1p was increased up to 4500 molecules per cell. Our results do not privilege the hypothesis of Yfh1p being an iron storage protein in vivo.
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Affiliation(s)
- Alexandra Seguin
- Laboratoire Mitochondries, Métaux et Stress oxydant, Institut Jacques Monod, CNRS-Université Paris Diderot, France
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20
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Marmolino D, Manto M, Acquaviva F, Vergara P, Ravella A, Monticelli A, Pandolfo M. PGC-1alpha down-regulation affects the antioxidant response in Friedreich's ataxia. PLoS One 2010; 5:e10025. [PMID: 20383327 PMCID: PMC2850922 DOI: 10.1371/journal.pone.0010025] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2010] [Accepted: 03/16/2010] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Cells from individuals with Friedreich's ataxia (FRDA) show reduced activities of antioxidant enzymes and cannot up-regulate their expression when exposed to oxidative stress. This blunted antioxidant response may play a central role in the pathogenesis. We previously reported that Peroxisome Proliferator Activated Receptor Gamma (PPARgamma) Coactivator 1-alpha (PGC-1alpha), a transcriptional master regulator of mitochondrial biogenesis and antioxidant responses, is down-regulated in most cell types from FRDA patients and animal models. METHODOLOGY/PRINCIPAL FINDINGS We used primary fibroblasts from FRDA patients and the knock in-knock out animal model for the disease (KIKO mouse) to determine basal superoxide dismutase 2 (SOD2) levels and the response to oxidative stress induced by the addition of hydrogen peroxide. We measured the same parameters after pharmacological stimulation of PGC-1alpha. Compared to control cells, PGC-1alpha and SOD2 levels were decreased in FRDA cells and did not change after addition of hydrogen peroxide. PGC-1alpha direct silencing with siRNA in control fibroblasts led to a similar loss of SOD2 response to oxidative stress as observed in FRDA fibroblasts. PGC-1alpha activation with the PPARgamma agonist (Pioglitazone) or with a cAMP-dependent protein kinase (AMPK) agonist (AICAR) restored normal SOD2 induction. Treatment of the KIKO mice with Pioglitazone significantly up-regulates SOD2 in cerebellum and spinal cord. CONCLUSIONS/SIGNIFICANCE PGC-1alpha down-regulation is likely to contribute to the blunted antioxidant response observed in cells from FRDA patients. This response can be restored by AMPK and PPARgamma agonists, suggesting a potential therapeutic approach for FRDA.
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Affiliation(s)
- Daniele Marmolino
- Laboratoire de Neurologie Expérimentale, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Mario Manto
- Laboratoire de Neurologie Expérimentale, Université Libre de Bruxelles (ULB), Brussels, Belgium
- Fonds National de la Recherche Scientifique (FNRS), Brussels, Belgium
| | - Fabio Acquaviva
- Department of Cellular and Molecular Biology, University of Naples “Federico II”, Naples, Italy
| | - Paola Vergara
- Department of Cellular and Molecular Biology, University of Naples “Federico II”, Naples, Italy
| | - Ajay Ravella
- Laboratoire de Neurologie Expérimentale, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | | | - Massimo Pandolfo
- Laboratoire de Neurologie Expérimentale, Université Libre de Bruxelles (ULB), Brussels, Belgium
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21
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Li H, Gakh O, Smith DY, Isaya G. Oligomeric yeast frataxin drives assembly of core machinery for mitochondrial iron-sulfur cluster synthesis. J Biol Chem 2009; 284:21971-21980. [PMID: 19491103 PMCID: PMC2755921 DOI: 10.1074/jbc.m109.011197] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Revised: 05/28/2009] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial biosynthesis of iron-sulfur clusters (ISCs) is a vital process involving the delivery of elemental iron and sulfur to a scaffold protein via molecular interactions that are still poorly defined. Analysis of highly conserved components of the yeast ISC assembly machinery shows that the iron-chaperone, Yfh1, and the sulfur-donor complex, Nfs1-Isd11, directly bind to each other. This interaction is mediated by direct Yfh1-Isd11 contacts. Moreover, both Yfh1 and Nfs1-Isd11 can directly bind to the scaffold, Isu1. Binding of Yfh1 to Nfs1-Isd11 or Isu1 requires oligomerization of Yfh1 and can occur in an iron-independent manner. However, more stable contacts are formed when Yfh1 oligomerization is normally coupled with the binding and oxidation of Fe2+. Our observations challenge the view that iron delivery for ISC synthesis is mediated by Fe2+-loaded monomeric Yfh1. Rather, we find that the iron oxidation-driven oligomerization of Yfh1 promotes the assembly of stable multicomponent complexes in which the iron donor and the sulfur donor simultaneously interact with each other as well as with the scaffold. Moreover, the ability to store ferric iron enables oligomeric Yfh1 to adjust iron release depending on the presence of Isu1 and the availability of elemental sulfur and reducing equivalents. In contrast, the use of anaerobic conditions that prevent Yfh1 oligomerization results in inhibition of ISC assembly on Isu1. These findings suggest that iron-dependent oligomerization is a mechanism by which the iron donor promotes assembly of the core machinery for mitochondrial ISC synthesis.
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Affiliation(s)
- Hongqiao Li
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905
| | - Oleksandr Gakh
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905
| | - Douglas Y. Smith
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905
| | - Grazia Isaya
- From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905
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22
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Bleackley MR, Wong AY, Hudson DM, Wu CHY, MacGillivray RT. Blood Iron Homeostasis: Newly Discovered Proteins and Iron Imbalance. Transfus Med Rev 2009; 23:103-23. [DOI: 10.1016/j.tmrv.2008.12.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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23
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Pandolfo M, Pastore A. The pathogenesis of Friedreich ataxia and the structure and function of frataxin. J Neurol 2009; 256 Suppl 1:9-17. [PMID: 19283345 DOI: 10.1007/s00415-009-1003-2] [Citation(s) in RCA: 168] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Understanding the role of frataxin in mitochondria is key to an understanding of the pathogenesis of Friedreich ataxia. Frataxins are small essential proteins whose deficiency causes a range of metabolic disturbances, which include oxidative stress, deficit of iron-sulphur clusters, and defects in heme synthesis, sulfur amino acid and energy metabolism, stress response, and mitochondrial function. Structural studies carried out on different orthologues have shown that the frataxin fold consists of a flexible N-terminal region present only in eukaryotes and in a highly conserved C-terminal globular domain. Frataxins bind iron directly but with very unusual properties: iron coordination is achieved solely by glutamates and aspartates exposed on the protein surface. It has been suggested that frataxin function is that of a ferritin-like protein, an iron chaperone of the iron sulphur cluster machinery and heme metabolism and/or a controller of cellular oxidative stress. To understand FRDA pathogenesis and to design novel therapeutic strategies, we must first precisely identify the cellular role of frataxin.
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Affiliation(s)
- Massimo Pandolfo
- Service de Neurologie, Hôpital Erasme - Université Libre de Bruxelles, Brussels, Belgium.
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24
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González-Cabo P, Llorens JV, Palau F, Moltó MD. Friedreich ataxia: an update on animal models, frataxin function and therapies. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 652:247-61. [PMID: 20225031 DOI: 10.1007/978-90-481-2813-6_17] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Friedreich ataxia (FRDA) is an autosomal recessive progressively debilitating degenerative disease that principally affects the nervous system and the heart. Although FRDA is considered a rare disease, is the most common inherited ataxia. It is caused by loss-of-function mutations in the FXN gene, mainly an expanded GAA triplet repeat in the intron 1. The genetic defect results in the reduction of frataxin levels, a protein targeted to the mitochondria. Frataxin deficiency leads to mitochondrial dysfunction, oxidative damage and iron accumulation. Studies of the yeast and animal models of the disease have led to propose several different roles for frataxin. Animal models have also been important for dissecting the steps of pathogenesis in FRDA and they are essential for the development of effective therapies. Currently, antioxidant and iron chelation therapies are under evaluation in clinical trials. Gene reactivation, gene therapy and protein replacement strategies for FRDA are promising approaches. This review focuses on the current models developed for FRDA, the different roles proposed for frataxin and the progress of potential treatment strategies for the disease.
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Affiliation(s)
- Pilar González-Cabo
- Laboratory of Genetics and Molecular Medicine, Instituto de Biomedicina de Valencia, CSIC, C/Jaume Roig 11, Valencia, Spain.
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25
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Gakh O, Smith DY, Isaya G. Assembly of the iron-binding protein frataxin in Saccharomyces cerevisiae responds to dynamic changes in mitochondrial iron influx and stress level. J Biol Chem 2008; 283:31500-10. [PMID: 18784075 PMCID: PMC2581586 DOI: 10.1074/jbc.m805415200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 09/08/2008] [Indexed: 11/06/2022] Open
Abstract
Defects in frataxin result in Friedreich ataxia, a genetic disease characterized by early onset of neurodegeneration, cardiomyopathy, and diabetes. Frataxin is a conserved mitochondrial protein that controls iron needed for iron-sulfur cluster assembly and heme synthesis and also detoxifies excess iron. Studies in vitro have shown that either monomeric or oligomeric frataxin delivers iron to other proteins, whereas ferritin-like frataxin particles convert redox-active iron to an inert mineral. We have investigated how these different forms of frataxin are regulated in vivo. In Saccharomyces cerevisiae, only monomeric yeast frataxin (Yfh1) was detected in unstressed cells when mitochondrial iron uptake was maintained at a steady, low nanomolar level. Increments in mitochondrial iron uptake induced stepwise assembly of Yfh1 species ranging from trimer to > or = 24-mer, independent of interactions between Yfh1 and its major iron-binding partners, Isu1/Nfs1 or aconitase. The rate-limiting step in Yfh1 assembly was a structural transition that preceded conversion of monomer to trimer. This step was induced, independently or synergistically, by mitochondrial iron increments, overexpression of wild type Yfh1 monomer, mutations that stabilize Yfh1 trimer, or heat stress. Faster assembly kinetics correlated with reduced oxidative damage and higher levels of aconitase activity, respiratory capacity, and cell survival. However, deregulation of Yfh1 assembly resulted in Yfh1 aggregation, aconitase sequestration, and mitochondrial DNA depletion. The data suggest that Yfh1 assembly responds to dynamic changes in mitochondrial iron uptake or stress exposure in a highly controlled fashion and that this may enable frataxin to simultaneously promote respiratory function and stress tolerance.
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Affiliation(s)
- Oleksandr Gakh
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905, USA
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26
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Levi S, Rovida E. The role of iron in mitochondrial function. Biochim Biophys Acta Gen Subj 2008; 1790:629-36. [PMID: 18948172 DOI: 10.1016/j.bbagen.2008.09.008] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 07/30/2008] [Accepted: 09/23/2008] [Indexed: 01/09/2023]
Abstract
BACKGROUND Iron is an essential element for life, as it is a cofactor for enzymes involved in many metabolic processes, but it can also be harmful, since its excess is thought to enhance the production of reactive oxygen species and induce oxidative damage. Iron is transformed into its biologically available form in the mitochondrion by the iron-sulfur (Fe/S) cluster and heme synthesis pathways. During the past decade, substantial progress has been made in the elucidation of iron-linked mechanisms that occur in the mitochondrion, demonstrating the crucial role played by this organelle in maintaining cellular iron homeostasis. GENERAL SIGNIFICANCE This review summarizes current knowledge of the mechanisms underlying iron trafficking in mitochondria and how it is handled inside the organelle. Relevant updates with regard to the Fe/S cluster and heme biosynthetic pathways, as well as the relationship between mitochondrial iron homeostasis impairment and related diseases, are also discussed.
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Affiliation(s)
- Sonia Levi
- Vita-Salute San Raffaele University, Via Olgettina 58, 20132, Milano, Italy.
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Schagerlöf U, Elmlund H, Gakh O, Nordlund G, Hebert H, Lindahl M, Isaya G, Al-Karadaghi S. Structural basis of the iron storage function of frataxin from single-particle reconstruction of the iron-loaded oligomer. Biochemistry 2008; 47:4948-54. [PMID: 18393441 PMCID: PMC3932613 DOI: 10.1021/bi800052m] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The mitochondrial protein frataxin plays a central role in mitochondrial iron homeostasis, and frataxin deficiency is responsible for Friedreich ataxia, a neurodegenerative and cardiac disease that affects 1 in 40000 children. Here we present a single-particle reconstruction from cryoelectron microscopic images of iron-loaded 24-subunit oligomeric frataxin particles at 13 and 17 A resolution. Computer-aided classification of particle images showed heterogeneity in particle size, which was hypothesized to result from gradual accumulation of iron within the core structure. Thus, two reconstructions were created from two classes of particles with iron cores of different sizes. The reconstructions show the iron core of frataxin for the first time. Compared to the previous reconstruction of iron-free particles from negatively stained images, the higher resolution of the present reconstruction allowed a more reliable analysis of the overall three-dimensional structure of the 24-meric assembly. This was done after docking the X-ray structure of the frataxin trimer into the EM reconstruction. The structure revealed a close proximity of the suggested ferroxidation sites of different monomers to the site proposed to serve in iron nucleation and mineralization. The model also assigns a new role to the N-terminal helix of frataxin in controlling the channel at the 4-fold axis of the 24-subunit oligomer. The reconstructions show that, together with some common features, frataxin has several unique features which distinguish it from ferritin. These include the overall organization of the oligomers, the way they are stabilized, and the mechanisms of iron core nucleation.
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Affiliation(s)
- Ulrika Schagerlöf
- Department of Molecular Biophysics, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Hans Elmlund
- Department of Molecular Biophysics, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
- Department of Biosciences and Nutrition, Karolinska Institutet and School of Technology and Health, Royal Institute of Technology, SE-14157 Huddinge, Sweden
| | - Oleksandr Gakh
- Departments of Pediatric and Adolescent Medicine and of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Gustav Nordlund
- Department of Molecular Biophysics, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Hans Hebert
- Department of Biosciences and Nutrition, Karolinska Institutet and School of Technology and Health, Royal Institute of Technology, SE-14157 Huddinge, Sweden
| | - Martin Lindahl
- Department of Molecular Biophysics, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
- Department of Biosciences and Nutrition, Karolinska Institutet and School of Technology and Health, Royal Institute of Technology, SE-14157 Huddinge, Sweden
| | - Grazia Isaya
- Departments of Pediatric and Adolescent Medicine and of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Salam Al-Karadaghi
- Departments of Pediatric and Adolescent Medicine and of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
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28
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Anderson PR, Kirby K, Orr WC, Hilliker AJ, Phillips JP. Hydrogen peroxide scavenging rescues frataxin deficiency in a Drosophila model of Friedreich's ataxia. Proc Natl Acad Sci U S A 2008; 105:611-6. [PMID: 18184803 PMCID: PMC2206584 DOI: 10.1073/pnas.0709691105] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Indexed: 11/18/2022] Open
Abstract
Friedreich's ataxia (FRDA) is a neurodegenerative disorder arising from a deficit of the mitochondrial iron chaperone, frataxin. Evidence primarily from yeast and mammalian cells is consistent with the hypothesis that a toxic hydroxyl radical generated from hydrogen peroxide (H2O2) via iron-catalyzed Fenton chemistry at least partially underlies the pathology associated with this disease. However, no whole-organism studies have been presented that directly test this hypothesis. We recently developed a Drosophila model that recapitulates the principal hallmarks of FRDA [Anderson PR, Kirby K, Hilliker A, Phillips JP (2005) Hum Mol Genet 14:3397-3405]. Using the Drosophila FRDA model, we now report that ectopic expression of enzymes that scavenge H2O2 suppresses the deleterious phenotypes associated with frataxin deficiency. In contrast, genetic augmentation with enzymes that scavenge superoxide is without effect. Augmentation of endogenous catalase restores the activity of the reactive oxygen species (ROS)-sensitive mitochondrial enzyme, aconitase and enhances resistance to H2O2 exposure, both of which are diminished by frataxin deficiency. Collectively, these data argue that H2O2 is an important pathogenic substrate underlying the phenotypes arising from frataxin deficiency in Drosophila and that interventions that reduce this specific ROS can effectively ameliorate these phenotypes. The therapeutic implications of these findings are clear and we believe warrant immediate clinical investigation.
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Affiliation(s)
- Peter R. Anderson
- *Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Kim Kirby
- *Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - William C. Orr
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75205; and
| | | | - John P. Phillips
- *Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
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29
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Bedekovics T, Gajdos GB, Kispal G, Isaya G. Partial conservation of functions between eukaryotic frataxin and the Escherichia coli frataxin homolog CyaY. FEMS Yeast Res 2007; 7:1276-84. [PMID: 17727661 DOI: 10.1111/j.1567-1364.2007.00296.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Frataxin is a mitochondrial protein structurally conserved from bacteria to humans. Eukaryotic frataxins are known to be involved in the maintenance of mitochondrial iron balance via roles in iron delivery and iron detoxification. The prokaryotic frataxin homolog, CyaY, has been shown to bind and donate iron for the assembly of [2Fe-2S] clusters in vitro. However, in contrast to the severe phenotypes associated with the partial or complete loss of frataxin in humans and other eukaryotes, deletion of the cyaY gene does not cause any obvious alteration of iron balance in bacterial cells, an effect that probably reflects functional redundancy between CyaY and other bacterial proteins. To study CyaY function in a nonredundant setting, we have expressed a mitochondria-targeted form of CyaY in a Saccharomyces cerevisiae strain depleted of the endogenous yeast frataxin protein (yfh1Delta). We show that in this strain CyaY complements to a large extent the loss of iron-sulfur cluster enzyme activities and heme synthesis, and thereby maintains a nearly normal respiratory growth. In addition, CyaY effectively protects yfh1Delta from oxidative damage during treatment with hydrogen peroxide but is less efficient in detoxifying excess labile iron during aerobic growth.
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Affiliation(s)
- Tibor Bedekovics
- Department of Biochemistry and Medical Chemistry, Faculty of Medicine, University of Pécs, Pécs, Hungary.
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30
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Harris JR. Negative staining across holes: application to fibril and tubular structures. Micron 2007; 39:168-76. [PMID: 17804247 DOI: 10.1016/j.micron.2007.07.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Revised: 07/19/2007] [Accepted: 07/19/2007] [Indexed: 10/23/2022]
Abstract
The negative staining technique, when used with holey carbon support films, presents superior imaging conditions than is the case when samples are adsorbed to continuous carbon films. A demonstration of this negative staining approach is presented, using ammonium molybdate in combination with trehalose, applied to several fibrillar and tubular samples. Fibrils formed from the amyloid-beta peptide and the protease inhibitor pepstain A spread very well unsupported across holes and the different polymorphic fibril forms can be readily assessed. However, tubular forms of amyloid-beta have a tendency to be flattened, due to surface tension forces prior to and during specimen drying. Sub-fibril assembly forms and D-banded rat tail type 1 collagen fibres are presented. The air-dried collagen images produced are shown to contain almost as much detail as those obtainable by cryo-negative staining. Fragile DNA and DNA-protein nanotubes are also shown to yield superior quality images to those produced on continuous carbon films. The iron-storage protein, frataxin, creates elongated oligomeric assemblies, containing bound ferrihydrite microcrystals. The iron particles within these flexuous oligomers can be defined in the presence of ammonium molybdate, but they are more readily demonstrated if the frataxin is spread across holes in the presence of trehalose alone. The samples used here serve to show the likely benefit obtainable from negative staining across holes for a range of other fibrillar and tubular samples in biology, medicine and nanobiotechnology.
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Affiliation(s)
- J Robin Harris
- Institute of Zoology, University of Mainz, D-55099 Mainz, Germany.
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31
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Popescu BFG, Pickering IJ, George GN, Nichol H. The chemical form of mitochondrial iron in Friedreich’s ataxia. J Inorg Biochem 2007; 101:957-66. [PMID: 17475338 DOI: 10.1016/j.jinorgbio.2007.03.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 03/09/2007] [Accepted: 03/14/2007] [Indexed: 01/08/2023]
Abstract
Friedreich's ataxia (FRDA) results from cellular damage caused by a deficiency in the mitochondrial matrix protein frataxin. To address the effect of frataxin deficiency on mitochondrial iron chemistry, the heavy mitochondrial fraction (HMF) was isolated from primary fibroblasts from FRDA affected and unaffected individuals. X-ray absorption spectroscopy was used to characterize the chemical form of iron. Near K-edge spectra were fitted with a series of model iron compounds to determine the proportion of each iron species. Most of the iron in both affected and unaffected fibroblasts was ferrihydrite. The iron K-edge from unaffected HMFs were best fitted with poorly organized ferrihydrite modeled by frataxin whereas HMFs from affected cells were best fitted with highly organized ferrihydrite modeled by ferritin. Both had several minor iron species but these did not differ consistently with disease. Since the iron K-edge spectra of ferritin and frataxin are very similar, we present additional evidence for the presence of ferritin-bound iron in HMF. The predominant ferritin subunit in HMFs from affected cells resembled mitochondrial ferritin (MtFt) in size and antigenicity. Western blotting of native gels showed that HMF from affected cells had 3-fold more holoferritin containing stainable iron. We conclude that most of the iron in fibroblast HMF from both affected and unaffected cells is ferrihydrite but only FRDA affected cells mineralize significant iron in mitochondrial ferritin.
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Affiliation(s)
- Bogdan F Gh Popescu
- Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Canada S7N5E5
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32
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Shan Y, Napoli E, Cortopassi G. Mitochondrial frataxin interacts with ISD11 of the NFS1/ISCU complex and multiple mitochondrial chaperones. Hum Mol Genet 2007; 16:929-41. [PMID: 17331979 DOI: 10.1093/hmg/ddm038] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The neurodegenerative disorder Friedreich's ataxia (FRDA) is caused by mutations in frataxin, a mitochondrial protein whose function remains controversial. Using co-immunoprecipitation and mass spectrometry we identified multiple interactors of mitochondrial frataxin in mammalian cells. One interactor was mortalin/GRP75, a homolog of the yeast ssq1 chaperone that integrates iron-sulfur clusters into imported mitochondrial proteins. Another interactor was ISD11, recently identified as a component of the eukaryotic complex Nfs1/ISCU, an essential component of iron-sulfur cluster biogenesis. Interactions between frataxin and ISD11, and frataxin and GRP75 were confirmed by co-immunoprecipitation experiments in both directions. Immunofluorescence analysis demonstrated that ISD11 co-localized with both frataxin and with mitochondria. The point mutations I154F and W155R in frataxin cause FRDA and are clustered to one surface of the protein, and these mutations decrease the interaction of frataxin with ISD11. The frataxin/ISD11 interaction was also decreased by the chelator EDTA, and was increased by supplementation with nickel but not other metal ions. Nickel supplementation rescued the defective interaction of mutant frataxin I154F and W155R with ISD11. Upon ISD11 depletion by siRNA in HEK293T cells, the amount of the Nfs1/ISCU protein complex declined, as did the activity of the iron-sulfur cluster enzyme aconitase, while the cellular iron content was increased, as seen in tissues from FRDA patients. Furthermore, ISD11 mRNA levels were decreased in FRDA patient cells. These data suggest that frataxin binds the iron-sulfur biogenesis Nfs1/ISCU complex through ISD11, that the interaction is nickel-dependent, and that multiple consequences of frataxin deficiency are duplicated by ISD11 deficiency.
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Affiliation(s)
- Yuxi Shan
- VM:Molecular Biosciences, 1311 Haring Hall, Davis, CA 95616, USA
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33
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Alves R, Sorribas A. In silico pathway reconstruction: Iron-sulfur cluster biogenesis in Saccharomyces cerevisiae. BMC SYSTEMS BIOLOGY 2007; 1:10. [PMID: 17408500 PMCID: PMC1839888 DOI: 10.1186/1752-0509-1-10] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Accepted: 01/31/2007] [Indexed: 01/17/2023]
Abstract
Background Current advances in genomics, proteomics and other areas of molecular biology make the identification and reconstruction of novel pathways an emerging area of great interest. One such class of pathways is involved in the biogenesis of Iron-Sulfur Clusters (ISC). Results Our goal is the development of a new approach based on the use and combination of mathematical, theoretical and computational methods to identify the topology of a target network. In this approach, mathematical models play a central role for the evaluation of the alternative network structures that arise from literature data-mining, phylogenetic profiling, structural methods, and human curation. As a test case, we reconstruct the topology of the reaction and regulatory network for the mitochondrial ISC biogenesis pathway in S. cerevisiae. Predictions regarding how proteins act in ISC biogenesis are validated by comparison with published experimental results. For example, the predicted role of Arh1 and Yah1 and some of the interactions we predict for Grx5 both matches experimental evidence. A putative role for frataxin in directly regulating mitochondrial iron import is discarded from our analysis, which agrees with also published experimental results. Additionally, we propose a number of experiments for testing other predictions and further improve the identification of the network structure. Conclusion We propose and apply an iterative in silico procedure for predictive reconstruction of the network topology of metabolic pathways. The procedure combines structural bioinformatics tools and mathematical modeling techniques that allow the reconstruction of biochemical networks. Using the Iron Sulfur cluster biogenesis in S. cerevisiae as a test case we indicate how this procedure can be used to analyze and validate the network model against experimental results. Critical evaluation of the obtained results through this procedure allows devising new wet lab experiments to confirm its predictions or provide alternative explanations for further improving the models.
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Affiliation(s)
- Rui Alves
- Departament de Ciencies Mediques Basiques, Universidad de Lleida, Montserrat Roig 2, 25008 Lleida, Spain
| | - Albert Sorribas
- Departament de Ciencies Mediques Basiques, Universidad de Lleida, Montserrat Roig 2, 25008 Lleida, Spain
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34
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Karlberg T, Schagerlöf U, Gakh O, Park S, Ryde U, Lindahl M, Leath K, Garman E, Isaya G, Al-Karadaghi S. The structures of frataxin oligomers reveal the mechanism for the delivery and detoxification of iron. Structure 2006; 14:1535-46. [PMID: 17027502 DOI: 10.1016/j.str.2006.08.010] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 08/21/2006] [Accepted: 08/28/2006] [Indexed: 10/24/2022]
Abstract
Defects in the mitochondrial protein frataxin are responsible for Friedreich ataxia, a neurodegenerative and cardiac disease that affects 1:40,000 children. Here, we present the crystal structures of the iron-free and iron-loaded frataxin trimers, and a single-particle electron microscopy reconstruction of a 24 subunit oligomer. The structures reveal fundamental aspects of the frataxin mechanism. The trimer has a central channel in which one atom of iron binds. Two conformations of the channel with different metal-binding affinities suggest that a gating mechanism controls whether the bound iron is delivered to other proteins or transferred to detoxification sites. The trimer constitutes the basic structural unit of the 24 subunit oligomer. The architecture of this oligomer and several features of the trimer structure demonstrate striking similarities to the iron-storage protein ferritin. The data reveal how stepwise assembly provides frataxin with the structural flexibility to perform two functions: metal delivery and detoxification.
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Affiliation(s)
- Tobias Karlberg
- Department of Molecular Biophysics, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
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35
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Bencze KZ, Kondapalli KC, Cook JD, McMahon S, Millán-Pacheco C, Pastor N, Stemmler TL. The structure and function of frataxin. Crit Rev Biochem Mol Biol 2006; 41:269-91. [PMID: 16911956 PMCID: PMC2859089 DOI: 10.1080/10409230600846058] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Frataxin, a highly conserved protein found in prokaryotes and eukaryotes, is required for efficient regulation of cellular iron homeostasis. Humans with a frataxin deficiency have the cardio- and neurodegenerative disorder Friedreich's ataxia, commonly resulting from a GAA trinucleotide repeat expansion in the frataxin gene. While frataxin's specific function remains a point of controversy, the general consensus is that the protein assists in controlling cellular iron homeostasis by directly binding iron. This review focuses on the structural and biochemical aspects of iron binding by the frataxin orthologs and outlines molecular attributes that may help explain the protein's role in different cellular pathways.
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Affiliation(s)
- Krisztina Z Bencze
- Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, Michigan 48201, USA
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36
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Abstract
Friedreich ataxia is the most common hereditary ataxia. The signs and symptoms of the disorder derive from decreased expression of the protein frataxin, which is involved in iron metabolism. Frataxin chaperones iron for iron-sulfur cluster biogenesis and detoxifies iron in the mitochondrial matrix. Decreased expression of frataxin is associated with impairments of iron-sulfur cluster biogenesis and heme synthesis, as well as with mitochondrial dysfunction and oxidative stress. Compounds currently in clinical trials are directed toward improving mitochondrial function and lessening oxidative stress. Iron chelators and compounds that increase frataxin expression are under evaluation. Further elucidation of frataxin's function should lead to additional therapeutic approaches.
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Affiliation(s)
- Robert B Wilson
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19106, USA.
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37
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Kauko A, Pulliainen AT, Haataja S, Meyer-Klaucke W, Finne J, Papageorgiou AC. Iron incorporation in Streptococcus suis Dps-like peroxide resistance protein Dpr requires mobility in the ferroxidase center and leads to the formation of a ferrihydrite-like core. J Mol Biol 2006; 364:97-109. [PMID: 16997323 DOI: 10.1016/j.jmb.2006.08.061] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 08/21/2006] [Accepted: 08/23/2006] [Indexed: 12/15/2022]
Abstract
The Dps-like peroxide resistance protein (Dpr) is a dodecameric protein that protects the human and swine pathogen Streptococcus suis from hydrogen peroxide by removing free Fe2+ from the cytosol. Subsequent oxidation of iron by Dpr results in the deposition of Fe3+ inside the protein's central cavity. Structural changes that occur in the ferroxidase center were studied by X-ray crystallography after soaking Dpr crystals with Fe2+ in the presence of sodium dithionite. Twelve iron-binding sites were identified with each site formed by residues Asp74 and Glu78 from one subunit, and Asp63, His47 and His59 from a 2-fold symmetry-related subunit. Compared to the iron-free Dpr, Asp74 and Glu78 were found to be the most flexible amino acid residues and able to adopt a variety of conformations in different subunits. The crystal structure of an Asp74Ala Dpr mutant soaked with a Fe2+ -solution revealed variations in the Asp63 position and no iron bound to the ferroxidase center. These results indicate an intrinsic flexibility in the active site that may be important for the catalytic reaction and subsequent nucleation events. Two iron cores with remarkably different features were identified in Dpr using X-ray absorption spectroscopy. Purified Dpr was found to have a small-size iron core with only approximately 16 iron atoms/dodecamer forming a ferritin-like ferrihydrite structure. Because of its size, this core represents the smallest iron core identified so far in ferritins and other Dps-like proteins. A large-size core (approximately 180 iron atoms/dodecamer) formed after incubating the protein with a ferrous solution shows differences in iron coordination compared to the small size core. Characterization of the two iron cores in Dpr could provide insights into nucleation events and the mechanism of iron core growth in the Dps family of proteins.
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Affiliation(s)
- Anni Kauko
- Turku Centre for Biotechnology, University of Turku and Abo Akademi University, BioCity, Turku, Finland
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38
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Castruita M, Saito M, Schottel PC, Elmegreen LA, Myneni S, Stiefel EI, Morel FMM. Overexpression and characterization of an iron storage and DNA-binding Dps protein from Trichodesmium erythraeum. Appl Environ Microbiol 2006; 72:2918-24. [PMID: 16597998 PMCID: PMC1449065 DOI: 10.1128/aem.72.4.2918-2924.2006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although the role of iron in marine productivity has received a great deal of attention, no iron storage protein has been isolated from a marine microorganism previously. We describe an Fe-binding protein belonging to the Dps family (DNA binding protein from starved cells) in the N(2)-fixing marine cyanobacterium Trichodesmium erythraeum. A dps gene encoding a protein with significant levels of identity to members of the Dps family was identified in the genome of T. erythraeum. This gene codes for a putative Dps(T. erythraeurm) protein (Dps(tery)) with 69% primary amino acid sequence similarity to Synechococcus DpsA. We expressed and purified Dps(tery), and we found that Dps(tery), like other Dps proteins, is able to bind Fe and DNA and protect DNA from degradation by DNase. We also found that Dps(tery) binds phosphate, like other ferritin family proteins. Fe K near-edge X-ray absorption of Dps(tery) indicated that it has an iron core that resembles that of horse spleen ferritin.
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Affiliation(s)
- M Castruita
- Department of Chemistry, Princeton University, 153A Guyot Hall, Princeton, NJ 08540, USA.
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39
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Cook JD, Bencze KZ, Jankovic AD, Crater AK, Busch CN, Bradley PB, Stemmler AJ, Spaller MR, Stemmler TL. Monomeric yeast frataxin is an iron-binding protein. Biochemistry 2006; 45:7767-77. [PMID: 16784228 PMCID: PMC2518068 DOI: 10.1021/bi060424r] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Friedreich's ataxia, an autosomal cardio- and neurodegenerative disorder that affects 1 in 50,000 humans, is caused by decreased levels of the protein frataxin. Although frataxin is nuclear-encoded, it is targeted to the mitochondrial matrix and necessary for proper regulation of cellular iron homeostasis. Frataxin is required for the cellular production of both heme and iron-sulfur (Fe-S) clusters. Monomeric frataxin binds with high affinity to ferrochelatase, the enzyme involved in iron insertion into porphyrin during heme production. Monomeric frataxin also binds to Isu, the scaffold protein required for assembly of Fe-S cluster intermediates. These processes (heme and Fe-S cluster assembly) share requirements for iron, suggesting that monomeric frataxin might function as the common iron donor. To provide a molecular basis to better understand frataxin's function, we have characterized the binding properties and metal-site structure of ferrous iron bound to monomeric yeast frataxin. Yeast frataxin is stable as an iron-loaded monomer, and the protein can bind two ferrous iron atoms with micromolar binding affinity. Frataxin amino acids affected by the presence of iron are localized within conserved acidic patches located on the surfaces of both helix-1 and strand-1. Under anaerobic conditions, bound metal is stable in the high-spin ferrous state. The metal-ligand coordination geometry of both metal-binding sites is consistent with a six-coordinate iron-(oxygen/nitrogen) based ligand geometry, surely constructed in part from carboxylate and possibly imidazole side chains coming from residues within these conserved acidic patches on the protein. On the basis of our results, we have developed a model for how we believe yeast frataxin interacts with iron.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Timothy L. Stemmler
- To whom correspondence should be sent: Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, 540 E. Canfield Ave., Detroit, MI 48201. Telephone: 313−577−5712, Fax: 313−577−2765, E-mail:
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40
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Frank P, DeTomaso A, Hedman B, Hodgson KO. A new structural motif for biological iron: iron K-edge XAS reveals a [Fe4-mu-(OR)5(OR)(9-10)] cluster in the ascidian Perophora annectens. Inorg Chem 2006; 45:3920-31. [PMID: 16676950 DOI: 10.1021/ic051445x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Phlebobranch ascidian Perophora annectens surprisingly exhibited a biological Fe/V ratio of approximately 15:1 on multichannel X-ray fluorescence analysis of two independent collections of organisms. Iron K-edge X-ray absorption spectroscopy (XAS) indicated a single form of iron. The XAS K-edge of the first collection of blood cells was shifted approximately +1 eV relative to that of the second, indicating redox activity with average iron oxidation states of 2.67+ and 2.60+. The first-derivative iron XAS K-edge features at 7120.5, 7124, and 7128 eV resembled the XAS of magnetite but not of ferritin or of dissolved Fe(II) or Fe(III). Pseudo-Voigt fits to blood-cell iron K-edge XAS spectra yielded 12.4 integrated units of preedge intensity, indicating a noncentrosymmetric environment. The non-phase-corrected extended X-ray absorption fine structure (EXAFS) Fourier transform spectrum showed a first-shell O/N peak at 1.55 angstroms and an intense Fe-Fe feature at 2.65 angstroms. Fits to the EXAFS required a split first shell with two O at 1.93 angstroms and three O at 2.07 angstroms, consistent with terminal and bridging alkoxide ligands, respectively. More distant shells included three C at 2.87 angstroms, two Fe at 3.08 angstroms, three O at 3.29 angstroms, and one Fe at 3.8 angstroms. Structural models consistent with these findings include a [Fe4(OR)13](2-/3-) broken-edged Fe4O5 cuboid or a [Fe4(OR)14](3-/4-) "Jacob's ladder" with three edge-fused Fe2(OR)2 rhombs. Either of these models represents an entirely new structural motif for biological iron. Vanadium domination of blood-cell metals cannot be a defining trait of Phlebobranch tunicates so long as P. annectens is included among them.
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Affiliation(s)
- Patrick Frank
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA
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Gakh O, Park S, Liu G, Macomber L, Imlay JA, Ferreira GC, Isaya G. Mitochondrial iron detoxification is a primary function of frataxin that limits oxidative damage and preserves cell longevity. Hum Mol Genet 2006; 15:467-79. [PMID: 16371422 DOI: 10.1093/hmg/ddi461] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Friedreich ataxia is a severe autosomal-recessive disease characterized by neurodegeneration, cardiomyopathy and diabetes, resulting from reduced synthesis of the mitochondrial protein frataxin. Although frataxin is ubiquitously expressed, frataxin deficiency leads to a selective loss of dorsal root ganglia neurons, cardiomyocytes and pancreatic beta cells. How frataxin normally promotes survival of these particular cells is the subject of intense debate. The predominant view is that frataxin sustains mitochondrial energy production and other cellular functions by providing iron for heme synthesis and iron-sulfur cluster (ISC) assembly and repair. We have proposed that frataxin not only promotes the biogenesis of iron-containing enzymes, but also detoxifies surplus iron thereby affording a critical anti-oxidant mechanism. These two functions have been difficult to tease apart, however, and the physiologic role of iron detoxification by frataxin has not yet been demonstrated in vivo. Here, we describe mutations that specifically impair the ferroxidation or mineralization activity of yeast frataxin, which are necessary for iron detoxification but do not affect the iron chaperone function of the protein. These mutations increase the sensitivity of yeast cells to oxidative stress, shortening chronological life span and precluding survival in the absence of the anti-oxidant enzyme superoxide dismutase. Thus, the role of frataxin is not limited to promoting ISC assembly or heme synthesis. Iron detoxification is another function of frataxin relevant to anti-oxidant defense and cell longevity that could play a critical role in the metabolically demanding environment of non-dividing neuronal, cardiac and pancreatic beta cells.
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Affiliation(s)
- Oleksandr Gakh
- Department of Pediatric, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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42
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Anderson PR, Kirby K, Hilliker AJ, Phillips JP. RNAi-mediated suppression of the mitochondrial iron chaperone, frataxin, in Drosophila. Hum Mol Genet 2005; 14:3397-405. [PMID: 16203742 DOI: 10.1093/hmg/ddi367] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The mitochondrial iron chaperone, frataxin, plays a critical role in cellular iron homeostasis and the synthesis and regeneration of Fe-S centers. Genetic insufficiency for frataxin is associated with Friedreich's Ataxia in humans and confers loss of function of Fe-containing proteins including components of the respiratory chain and mitochondrial and cytosolic aconitases. Here, we report the use of RNA-interference (RNAi) to suppress frataxin in the multicellular eukaryote, Drosophila. Phenotypically, suppression of the Drosophila frataxin homologue (dfh) confers distinct phenotypes in larvae and adults, leading to giant long-lived larvae and to conditional short-lived adults. Deficiency of the DFH protein results in diminished activities of numerous heme- and iron-sulfur-containing enzymes, loss of intracellular iron homeostasis and increased susceptibility to iron toxicity. In parallel with the differential larval and adult phenotypes, our results indicate that dfh silencing differentially dysregulates ferritin expression in adults but not in larvae. Moreover, silencing of dfh in the peripheral nervous system, a specific focus of Friedreich's pathology, permits normal larval development but imposes a marked reduction in adult lifespan. In contrast, dfh silencing in motorneurons has no deleterious effect in either larvae or adults. Finally, overexpression of Sod1, Sod2 or Cat does not suppress the failure of DFH-deficient animals to successfully complete eclosion, suggesting a minimal role of oxidative stress in this phenotype. The robust developmental, biochemical and tissue-specific phenotypes conferred by DFH deficiency in Drosophila provide a platform for identifying genetic, nutritional and environmental factors, which ameliorate the symptoms arising from frataxin deficiency.
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Affiliation(s)
- Peter R Anderson
- Department of Molecular and Cellular Biology, University of Guelph, Ontario, Canada
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43
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Fenske D, Gnida M, Schneider K, Meyer-Klaucke W, Schemberg J, Henschel V, Meyer AK, Knöchel A, Müller A. A new type of metalloprotein: The Mo storage protein from azotobacter vinelandii contains a polynuclear molybdenum-oxide cluster. Chembiochem 2005; 6:405-13. [PMID: 15651045 DOI: 10.1002/cbic.200400263] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Azotobacter vinelandii is a diazotrophic bacterium characterized by the outstanding capability of storing Mo in a special storage protein, which guarantees Mo-dependent nitrogen fixation even under growth conditions of extreme Mo starvation. The Mo storage protein is constitutively synthesized with respect to the nitrogen source and is regulated by molybdenum at an extremely low concentration level (0-50 nM). This protein was isolated as an alpha4beta4 octamer with a total molecular mass of about 240 kg mol(-1) and its shape was determined by small-angle X-ray scattering. The genes of the alpha and beta subunits were unequivocally identified; the amino acid sequences thereby determined reveal that the Mo storage protein is not related to any other known molybdoprotein. Each protein molecule can store at least 90 Mo atoms. Extended X-ray absorption fine-structure spectroscopy identified a metal-oxygen cluster bound to the Mo storage protein. The binding of Mo (biosynthesis and incorporation of the cluster) is dependent on adenosine triphosphate (ATP); Mo release is ATP-independent but pH-regulated, occurring only above pH 7.1. This Mo storage protein is the only known noniron metal storage system in the biosphere containing a metal-oxygen cluster.
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Affiliation(s)
- Dirk Fenske
- Lehrstuhl für Anorganische Chemie I, Universität Bielefeld, Universitätsstrasse 25, 33615 Bielefeld, Germany
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Calabrese V, Lodi R, Tonon C, D'Agata V, Sapienza M, Scapagnini G, Mangiameli A, Pennisi G, Stella AMG, Butterfield DA. Oxidative stress, mitochondrial dysfunction and cellular stress response in Friedreich's ataxia. J Neurol Sci 2005; 233:145-62. [PMID: 15896810 DOI: 10.1016/j.jns.2005.03.012] [Citation(s) in RCA: 279] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
There is significant evidence that the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, Friedreich's ataxia (FRDA), multiple sclerosis and amyotrophic lateral sclerosis, may involve the generation of reactive oxygen species (ROS) and/or reactive nitrogen species (RNS) associated with mitochondrial dysfunction. The mitochondrial genome may play an essential role in the pathogenesis of these diseases, and evidence for mitochondria being a site of damage in neurodegenerative disorders is based in part on observed decreases in the respiratory chain complex activities in Parkinson's, Alzheimer's, and Huntington's disease. Such defects in respiratory complex activities, possibly associated with oxidant/antioxidant imbalance, are thought to underlie defects in energy metabolism and induce cellular degeneration. The precise sequence of events in FRDA pathogenesis is uncertain. The impaired intramitochondrial metabolism with increased free iron levels and a defective mitochondrial respiratory chain, associated with increased free radical generation and oxidative damage, may be considered possible mechanisms that compromise cell viability. Recent evidence suggests that frataxin might detoxify ROS via activation of glutathione peroxidase and elevation of thiols, and in addition, that decreased expression of frataxin protein is associated with FRDA. Many approaches have been undertaken to understand FRDA, but the heterogeneity of the etiologic factors makes it difficult to define the clinically most important factor determining the onset and progression of the disease. However, increasing evidence indicates that factors such as oxidative stress and disturbed protein metabolism and their interaction in a vicious cycle are central to FRDA pathogenesis. Brains of FRDA patients undergo many changes, such as disruption of protein synthesis and degradation, classically associated with the heat shock response, which is one form of stress response. Heat shock proteins are proteins serving as molecular chaperones involved in the protection of cells from various forms of stress. In the central nervous system, heat shock protein (HSP) synthesis is induced not only after hyperthermia, but also following alterations in the intracellular redox environment. The major neurodegenerative diseases, Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), Huntington's disease (HD) and FRDA are all associated with the presence of abnormal proteins. Among the various HSPs, HSP32, also known as heme oxygenase I (HO-1), has received considerable attention, as it has been recently demonstrated that HO-1 induction, by generating the vasoactive molecule carbon monoxide and the potent antioxidant bilirubin, could represent a protective system potentially active against brain oxidative injury. Given the broad cytoprotective properties of the heat shock response there is now strong interest in discovering and developing pharmacological agents capable of inducing the heat shock response. This may open up new perspectives in medicine, as molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. In particular, manipulation of endogenous cellular defense mechanisms, such as the heat shock response, through nutritional antioxidants, pharmacological compounds or gene transduction, may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration.
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Affiliation(s)
- Vittorio Calabrese
- Section of Biochemistry and Molecular Biology, Department of Chemistry, Faculty of Medicine, University of Catania, Catania, Viale Andrea Doria 6, 95100 Catania, Italy.
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González-Cabo P, Vázquez-Manrique RP, García-Gimeno MA, Sanz P, Palau F. Frataxin interacts functionally with mitochondrial electron transport chain proteins. Hum Mol Genet 2005; 14:2091-8. [PMID: 15961414 DOI: 10.1093/hmg/ddi214] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Frataxin deficiency is the main cause of Friedreich ataxia, an autosomal recessive neurodegenerative disorder. Frataxin function in mitochondria has not been fully explained yet. In this work, we show that Saccharomyces cerevisiae frataxin orthologue Yfh1p interacts physically with succinate dehydrogenase complex subunits Sdh1p and Sdh2p of the yeast mitochondrial electron transport chain and also with electron transfer flavoprotein complex ETFalpha and ETFbeta subunits from the electron transfer flavoprotein complex. Genetic synthetic interaction experiments confirmed a functional relationship between YFH1 and succinate dehydrogenase genes SDH1 and SDH2. We also demonstrate a physical interaction between human frataxin and human succinate dehydrogenase complex subunits, suggesting also a key role of frataxin in the mitochondrial electron transport chain in humans. Consequently, we suggest a direct participation of the respiratory chain in the pathogenesis of the Friedreich ataxia, which we propose to be considered as an OXPHOS disease.
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Affiliation(s)
- Pilar González-Cabo
- Department of Genomics and Proteomics, Instituto de Biomedicina, CSIC, C/Jaume Roig 11, 46010 Valencia, Spain
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O'Neill HA, Gakh O, Isaya G. Supramolecular assemblies of human frataxin are formed via subunit-subunit interactions mediated by a non-conserved amino-terminal region. J Mol Biol 2005; 345:433-9. [PMID: 15581888 DOI: 10.1016/j.jmb.2004.10.074] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2004] [Revised: 10/21/2004] [Accepted: 10/22/2004] [Indexed: 11/30/2022]
Abstract
The mitochondrial protein frataxin is emerging as a novel mechanism to promote iron metabolism while also providing anti-oxidant protection. Recombinant frataxin proteins from different species are able to form large molecular assemblies that store Fe(III) as a stable mineral in vitro. Furthermore, monomeric and assembled forms of frataxin donate Fe(II) to the Fe-S cluster scaffold protein IscU, [3Fe-4S]1+ aconitase, and ferrochelatase in vitro. However, little is known about the speciation of frataxin in vivo, and the physiologically relevant form(s) of the protein remains undefined. Here, we report that human heart mitochondria contain frataxin species of increasing negative surface charge and molecular mass, ranging from monomer to polymers of >1 MDa. Moreover, we show that the main partner protein of frataxin, IscU, binds in a stable manner to frataxin oligomers. These results suggest that assembly is a physiologic property of frataxin. Biochemical analyses further reveal that, unlike the prokaryotic and yeast frataxin homologues, which require iron-protein interactions for assembly, human frataxin uses stable subunit-subunit interactions involving a non-conserved amino-terminal region. We propose that human frataxin is a modular protein that depends on self-assembly to accomplish its diverse functions.
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Affiliation(s)
- Heather A O'Neill
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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47
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Abstract
The ability of iron to cycle between Fe(2+) and Fe(3+) forms has led to the evolution, in different forms, of several iron-containing protein cofactors that are essential for a wide variety of cellular processes, to the extent that virtually all cells require iron for survival and prosperity. The redox properties of iron, however, also mean that this metal is potentially highly toxic and this, coupled with the extreme insolubility of Fe(3+), presents the cell with the significant problem of how to maintain this essential metal in a safe and bioavailable form. This has been overcome through the evolution of proteins capable of reversibly storing iron in the form of a Fe(3+) mineral. For several decades the ferritins have been synonymous with the function of iron storage. Within this family are subfamilies of mammalian, plant and bacterial ferritins which are all composed of 24 subunits assembled to form an essentially spherical protein with a central cavity in which the mineral is laid down. In the past few years it has become clear that other proteins, belonging to the family of DNA-binding proteins from starved cells (the Dps family), which are oligomers of 12 subunits, and to the frataxin family, which may contain up to 48 subunits, are also able to lay down a Fe(3+) mineral core. Here we present an overview of the formation of protein-coated iron minerals, with particular emphasis on the structures of the protein coats and the mechanisms by which they promote core formation. We show on the one hand that significant mechanistic similarities exist between structurally dissimilar proteins, while on the other that relatively small structural differences between otherwise similar proteins result in quite dramatic mechanistic differences.
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Affiliation(s)
- Allison Lewin
- Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, UK.
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48
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Bou-Abdallah F, Adinolfi S, Pastore A, Laue TM, Dennis Chasteen N. Iron binding and oxidation kinetics in frataxin CyaY of Escherichia coli. J Mol Biol 2004; 341:605-15. [PMID: 15276847 DOI: 10.1016/j.jmb.2004.05.072] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2004] [Revised: 05/25/2004] [Accepted: 05/27/2004] [Indexed: 11/28/2022]
Abstract
Friedreich's ataxia is associated with a deficiency in frataxin, a conserved mitochondrial protein of unknown function. Here, we investigate the iron binding and oxidation chemistry of Escherichia coli frataxin (CyaY), a homologue of human frataxin, with the aim of better understanding the functional properties of this protein. Anaerobic isothermal titration calorimetry (ITC) demonstrates that at least two ferrous ions bind specifically but relatively weakly per CyaY monomer (K(d) approximately 4 microM). Such weak binding is consistent with the hypothesis that the protein functions as an iron chaperone. The bound Fe(II) is oxidized slowly by O(2). However, oxidation occurs rapidly and completely with H(2)O(2) through a non-enzymatic process with a stoichiometry of two Fe(II)/H(2)O(2), indicating complete reduction of H(2)O(2) to H(2)O. In accord with this stoichiometry, electron paramagnetic resonance (EPR) spin trapping experiments indicate that iron catalyzed production of hydroxyl radical from Fenton chemistry is greatly attenuated in the presence of CyaY. The Fe(III) produced from oxidation of Fe(II) by H(2)O(2) binds to the protein with a stoichiometry of six Fe(III)/CyaY monomer as independently measured by kinetic, UV-visible, fluorescence, iron analysis and pH-stat titrations. However, as many as 25-26 Fe(III)/monomer can bind to the protein, exhibiting UV absorption properties similar to those of hydrolyzed polynuclear Fe(III) species. Analytical ultracentrifugation measurements indicate that a tetramer is formed when Fe(II) is added anaerobically to the protein; multiple protein aggregates are formed upon oxidation of the bound Fe(II). The observed iron oxidation and binding properties of frataxin CyaY may afford the mitochondria protection against iron-induced oxidative damage.
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Affiliation(s)
- Fadi Bou-Abdallah
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA
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49
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Bulteau AL, O'Neill HA, Kennedy MC, Ikeda-Saito M, Isaya G, Szweda LI. Frataxin acts as an iron chaperone protein to modulate mitochondrial aconitase activity. Science 2004; 305:242-5. [PMID: 15247478 DOI: 10.1126/science.1098991] [Citation(s) in RCA: 289] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Numerous degenerative disorders are associated with elevated levels of prooxidants and declines in mitochondrial aconitase activity. Deficiency in the mitochondrial iron-binding protein frataxin results in diminished activity of various mitochondrial iron-sulfur proteins including aconitase. We found that aconitase can undergo reversible citrate-dependent modulation in activity in response to pro-oxidants. Frataxin interacted with aconitase in a citrate-dependent fashion, reduced the level of oxidant-induced inactivation, and converted inactive [3Fe-4S]1+ enzyme to the active [4Fe-4S]2+ form of the protein. Thus, frataxin is an iron chaperone protein that protects the aconitase [4Fe-4S]2+ cluster from disassembly and promotes enzyme reactivation.
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Affiliation(s)
- Anne-Laure Bulteau
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
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50
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Abstract
Mitochondria generate adenosine triphosphate (ATP) but also dangerous reactive oxygen species (ROS). One-electron reduction of dioxygen in the early stages of the electron transport chain yields a superoxide radical that is detoxified by mitochondrial superoxide dismutase to give hydrogen peroxide. The hydroxyl radical is derived from decomposition of hydrogen peroxide via the Fenton reaction, catalyzed by Fe2+ ions. Mitochondria require a constant supply of Fe2+ for heme and iron-sulfur cluster biosyntheses and therefore are particularly susceptible to ROS attack. Two main antioxidant defenses are known in mitochondria: enzymes that catalytically remove ROS, e.g. superoxide dismutase and glutathione peroxidase, and low molecular weight agents that scavenge ROS, including coenzyme Q, glutathione, and vitamins E and C. An effective defensive system, however, should also involve means to control the availability of pro-oxidants such as Fe2+ ions. There is increasing evidence that this function may be carried out by the mitochondrial protein frataxin. Frataxin deficiency is the primary cause of Friedreich's ataxia (FRDA), an autosomal recessive degenerative disease. Frataxin is a highly conserved mitochondrial protein that plays a critical role in iron homeostasis. Respiratory deficits, abnormal cellular iron distribution and increased oxidative damage are associated with frataxin defects in yeast and mouse models of FRDA. The mechanism by which frataxin regulates iron metabolism is unknown. The yeast frataxin homologue (mYfh1p) is activated by Fe(II) in the presence of oxygen and assembles stepwise into a 48-subunit multimer (alpha48) that sequesters >2000 atoms of iron in a ferrihydrite mineral core. Assembly of mYfhlp is driven by two sequential iron oxidation reactions: a fast ferroxidase reaction catalyzed by mYfh1p induces the first assembly step (alpha --> alpha3), followed by a slower autoxidation reaction that promotes the assembly of higher order oligomers yielding alpha48. Depending on the ionic environment, stepwise assembly is associated with the sequestration of < or = 50-75 Fe(II)/subunit. This Fe(II) is initially loosely bound to mYfh1p and can be readily mobilized by chelators or made available to the mitochondrial enzyme ferrochelatase to synthesize heme. However, as iron oxidation and mineralization proceed, Fe(III) becomes progressively inaccessible and a stable iron-protein complex is produced. In conclusion, by coupling iron oxidation with stepwise assembly, frataxin can successively function as an iron chaperon or an iron store. Reduced iron availability and solubility and increased oxidative damage may therefore explain the pathogenesis of FRDA.
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Affiliation(s)
- G Isaya
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
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