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Vishwanathan V, D’Silva P. Loss of Function of mtHsp70 Chaperone Variants Leads to Mitochondrial Dysfunction in Congenital Sideroblastic Anemia. Front Cell Dev Biol 2022; 10:847045. [PMID: 35252210 PMCID: PMC8888832 DOI: 10.3389/fcell.2022.847045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Accepted: 01/31/2022] [Indexed: 11/13/2022] Open
Abstract
Congenital Sideroblastic Anemias (CSA) is a group of rare genetic disorders characterized by the abnormal accumulation of iron in erythrocyte precursors. A common hallmark underlying these pathological conditions is mitochondrial dysfunction due to altered protein homeostasis, heme biosynthesis, and oxidative phosphorylation. A clinical study on congenital sideroblastic anemia has identified mutations in mitochondrial Hsp70 (mtHsp70/Mortalin). Mitochondrial Hsp70 plays a critical role in maintaining mitochondrial function by regulating several pathways, including protein import and folding, and iron-sulfur cluster synthesis. Owing to the structural and functional homology between human and yeast mtHsp70, we have utilized the yeast system to delineate the role of mtHsp70 variants in the etiology of CSA’s. Analogous mutations in yeast mtHsp70 exhibited temperature-sensitive growth phenotypes under non-respiratory and respiratory conditions. In vivo analyses indicate a perturbation in mitochondrial mass and functionality accompanied by an alteration in the organelle network and cellular redox levels. Preliminary in vitro biochemical studies of mtHsp70 mutants suggest impaired import function, altered ATPase activity and substrate interaction. Together, our findings suggest the loss of chaperone activity to be a pivotal factor in the pathophysiology of congenital sideroblastic anemia.
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2
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Wang J, Chen J, Hu Y, Ying SH, Feng MG. Roles of six Hsp70 genes in virulence, cell wall integrity, antioxidant activity and multiple stress tolerance of Beauveria bassiana. Fungal Genet Biol 2020; 144:103437. [DOI: 10.1016/j.fgb.2020.103437] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/25/2020] [Accepted: 07/19/2020] [Indexed: 12/31/2022]
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3
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Srivastava S, Vishwanathan V, Birje A, Sinha D, D'Silva P. Evolving paradigms on the interplay of mitochondrial Hsp70 chaperone system in cell survival and senescence. Crit Rev Biochem Mol Biol 2020; 54:517-536. [PMID: 31997665 DOI: 10.1080/10409238.2020.1718062] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The role of mitochondria within a cell has grown beyond being the prime source of cellular energy to one of the major signaling platforms. Recent evidence provides several insights into the crucial roles of mitochondrial chaperones in regulating the organellar response to external triggers. The mitochondrial Hsp70 (mtHsp70/Mortalin/Grp75) chaperone system plays a critical role in the maintenance of proteostasis balance in the organelle. Defects in mtHsp70 network result in attenuated protein transport and misfolding of polypeptides leading to mitochondrial dysfunction. The functions of Hsp70 are primarily governed by J-protein cochaperones. Although human mitochondria possess a single Hsp70, its multifunctionality is characterized by the presence of multiple specific J-proteins. Several studies have shown a potential association of Hsp70 and J-proteins with diverse pathological states that are not limited to their canonical role as chaperones. The role of mitochondrial Hsp70 and its co-chaperones in disease pathogenesis has not been critically reviewed in recent years. We evaluated some of the cellular interfaces where Hsp70 machinery associated with pathophysiological conditions, particularly in context of tumorigenesis and neurodegeneration. The mitochondrial Hsp70 machinery shows a variable localization and integrates multiple components of the cellular processes with varied phenotypic consequences. Although Hsp70 and J-proteins function synergistically in proteins folding, their precise involvement in pathological conditions is mainly idiosyncratic. This machinery is associated with a heterogeneous set of molecules during the progression of a disorder. However, the precise binding to the substrate for a specific physiological response under a disease subtype is still an undocumented area of analysis.
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Affiliation(s)
- Shubhi Srivastava
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | | | - Abhijit Birje
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Devanjan Sinha
- Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi, India
| | - Patrick D'Silva
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
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4
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Jiang H, Horwitz AA, Wright C, Tai A, Znameroski EA, Tsegaye Y, Warbington H, Bower BS, Alves C, Co C, Jonnalagadda K, Platt D, Walter JM, Natarajan V, Ubersax JA, Cherry JR, Love JC. Challenging the workhorse: Comparative analysis of eukaryotic micro-organisms for expressing monoclonal antibodies. Biotechnol Bioeng 2019; 116:1449-1462. [PMID: 30739333 PMCID: PMC6836876 DOI: 10.1002/bit.26951] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 01/31/2019] [Accepted: 02/06/2019] [Indexed: 01/09/2023]
Abstract
For commercial protein therapeutics, Chinese hamster ovary (CHO) cells have an established history of safety, proven capability to express a wide range of therapeutic proteins and high volumetric productivities. Expanding global markets for therapeutic proteins and increasing concerns for broadened access of these medicines has catalyzed consideration of alternative approaches to this platform. Reaching these objectives likely will require an order of magnitude increase in volumetric productivity and a corresponding reduction in the costs of manufacture. For CHO-based manufacturing, achieving this combination of targeted improvements presents challenges. Based on a holistic analysis, the choice of host cells was identified as the single most influential factor for both increasing productivity and decreasing costs. Here we evaluated eight wild-type eukaryotic micro-organisms with prior histories of recombinant protein expression. The evaluation focused on assessing the potential of each host, and their corresponding phyla, with respect to key attributes relevant for manufacturing, namely (a) growth rates in industry-relevant media, (b) adaptability to modern techniques for genome editing, and (c) initial characterization of product quality. These characterizations showed that multiple organisms may be suitable for production with appropriate engineering and development and highlighted that yeast in general present advantages for rapid genome engineering and development cycles.
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Affiliation(s)
- Hanxiao Jiang
- Research and Development, Amyris Inc., Emeryville, California
| | | | - Chapman Wright
- Engineering & Technology, Biogen, Cambridge, Massachusetts
| | - Anna Tai
- Research and Development, Amyris Inc., Emeryville, California
| | | | - Yoseph Tsegaye
- Research and Development, Amyris Inc., Emeryville, California
| | | | | | | | - Carl Co
- Engineering & Technology, Biogen, Cambridge, Massachusetts
| | | | - Darren Platt
- Research and Development, Amyris Inc., Emeryville, California
| | | | | | | | - Joel R Cherry
- Research and Development, Amyris Inc., Emeryville, California
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Nyakundi DO, Bentley SJ, Boshoff A. Hsp70 Escort Protein: More Than a Regulator of Mitochondrial Hsp70. CURR PROTEOMICS 2018. [DOI: 10.2174/1570164615666180713104919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Hsp70 members occupy a central role in proteostasis and are found in different eukaryotic
cellular compartments. The mitochondrial Hsp70/J-protein machinery performs multiple functions vital
for the proper functioning of the mitochondria, including forming part of the import motor that
transports proteins from the cytosol into the matrix and inner membrane, and subsequently folds these
proteins in the mitochondria. However, unlike other Hsp70s, mitochondrial Hsp70 (mtHsp70) has the
propensity to self-aggregate, accumulating as insoluble aggregates. The self-aggregation of mtHsp70 is
caused by both interdomain and intramolecular communication within the ATPase and linker domains.
Since mtHsp70 is unable to fold itself into an active conformation, it requires an Hsp70 escort protein
(Hep) to both inhibit self-aggregation and promote the correct folding. Hep1 orthologues are present in
the mitochondria of many eukaryotic cells but are absent in prokaryotes. Hep1 proteins are relatively
small and contain a highly conserved zinc-finger domain with one tetracysteine motif that is essential
for binding zinc ions and maintaining the function and solubility of the protein. The zinc-finger domain
lies towards the C-terminus of Hep1 proteins, with very little conservation outside of this domain.
Other than maintaining mtHsp70 in a functional state, Hep1 proteins play a variety of other roles in the
cell and have been proposed to function as both chaperones and co-chaperones. The cellular
localisation and some of the functions are often speculative and are not common to all Hep1 proteins
analysed to date.
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Affiliation(s)
- David O. Nyakundi
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
| | - Stephen J. Bentley
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
| | - Aileen Boshoff
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
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Penna C, Sorge M, Femminò S, Pagliaro P, Brancaccio M. Redox Aspects of Chaperones in Cardiac Function. Front Physiol 2018; 9:216. [PMID: 29615920 PMCID: PMC5864891 DOI: 10.3389/fphys.2018.00216] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 02/26/2018] [Indexed: 12/14/2022] Open
Abstract
Molecular chaperones are stress proteins that allow the correct folding or unfolding as well as the assembly or disassembly of macromolecular cellular components. Changes in expression and post-translational modifications of chaperones have been linked to a number of age- and stress-related diseases including cancer, neurodegeneration, and cardiovascular diseases. Redox sensible post-translational modifications, such as S-nitrosylation, glutathionylation and phosphorylation of chaperone proteins have been reported. Redox-dependent regulation of chaperones is likely to be a phenomenon involved in metabolic processes and may represent an adaptive response to several stress conditions, especially within mitochondria, where it impacts cellular bioenergetics. These post-translational modifications might underlie the mechanisms leading to cardioprotection by conditioning maneuvers as well as to ischemia/reperfusion injury. In this review, we discuss this topic and focus on two important aspects of redox-regulated chaperones, namely redox regulation of mitochondrial chaperone function and cardiac protection against ischemia/reperfusion injury.
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Affiliation(s)
- Claudia Penna
- Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Matteo Sorge
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Saveria Femminò
- Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Pasquale Pagliaro
- Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Mara Brancaccio
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
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Molecular Chaperones: Structure-Function Relationship and their Role in Protein Folding. REGULATION OF HEAT SHOCK PROTEIN RESPONSES 2018. [DOI: 10.1007/978-3-319-74715-6_8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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8
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Liu Z, Wang Z, Huang M, Yan L, Ma Z, Yin Y. The FgSsb-FgZuo-FgSsz complex regulates multiple stress responses and mycotoxin production via folding the soluble SNARE Vam7 and β2-tubulin in Fusarium graminearum. Environ Microbiol 2017; 19:5040-5059. [PMID: 29076607 DOI: 10.1111/1462-2920.13968] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 10/16/2017] [Accepted: 10/19/2017] [Indexed: 11/28/2022]
Abstract
Hsp70 proteins play important roles in protein folding in the budding yeast, but their functions in pathogenic fungi are largely unknown. Here, we found that Fusarium graminearum Hsp70 proteins FgSsb, FgSsz and their cochaperone FgZuo formed a complex. This complex was required for microtubule morphology, vacuole fusion and endocytosis. More importantly, the β2-tubulin FgTub2 and SNARE protein FgVam7 were identified as targeting proteins of this complex. We further found that the complex FgSsb-FgZuo-FgSsz controlled sensitivity of F. graminearum to the antimicrotubule drug carbendazim and cold stress via regulating the folding of FgTub2. Moreover, this complex assisted the folding of FgVam7, subsequently modulated vacuole fusion and responses to heavy metal, osmotic and oxidative stresses. In addition, the deletion of this complex led to dramatically decreased deoxynivalenol biosynthesis. This study uncovers a novel regulating mechanism of Hsp70 in multiple stress responses in a filamentous fungus.
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Affiliation(s)
- Zunyong Liu
- Institute of Biotechnology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Zhihui Wang
- Institute of Biotechnology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Mengmeng Huang
- Institute of Biotechnology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Leiyan Yan
- Ningbo Academy of Agricultural Sciences, Ningbo, 315040, China
| | - Zhonghua Ma
- Institute of Biotechnology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.,State Key Laboratory of Rice Biology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Yanni Yin
- Institute of Biotechnology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
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9
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Mitochondrial Cochaperone Mge1 Is Involved in Regulating Susceptibility to Fluconazole in Saccharomyces cerevisiae and Candida Species. mBio 2017; 8:mBio.00201-17. [PMID: 28720726 PMCID: PMC5516249 DOI: 10.1128/mbio.00201-17] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
MGE1 encodes a yeast chaperone involved in Fe-S cluster metabolism and protein import into the mitochondria. In this study, we identified MGE1 as a multicopy suppressor of susceptibility to the antifungal fluconazole in the model yeast Saccharomyces cerevisiae. We demonstrate that this phenomenon is not exclusively dependent on the integrity of the mitochondrial DNA or on the presence of the drug efflux pump Pdr5. Instead, we show that the increased dosage of Mge1 plays a protective role by retaining increased amounts of ergosterol upon fluconazole treatment. Iron metabolism and, more particularly, Fe-S cluster formation are involved in regulating this process, since the responsible Hsp70 chaperone, Ssq1, is required. Additionally, we show the necessity but, by itself, insufficiency of activating the iron regulon in establishing the Mge1-related effect on drug susceptibility. Finally, we confirm a similar role for Mge1 in fluconazole susceptibility in the pathogenic fungi Candida glabrata and Candida albicans. Although they are mostly neglected compared to bacterial infections, fungal infections pose a serious threat to the human population. While some of them remain relatively harmless, infections that reach the bloodstream often become lethal. Only a few therapies are available, and resistance of the pathogen to these drugs is a frequently encountered problem. It is thus essential that more research is performed on how these pathogens cope with the treatment and cause recurrent infections. Baker’s yeast is often used as a model to study pathogenic fungi. We show here, by using this model, that iron metabolism and the formation of the important iron-sulfur clusters are involved in regulating susceptibility to fluconazole, the most commonly used antifungal drug. We show that the same process likely also occurs in two of the most regularly isolated pathogenic fungi, Candida glabrata and Candida albicans.
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10
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Caslavka Zempel KE, Vashisht AA, Barshop WD, Wohlschlegel JA, Clarke SG. Determining the Mitochondrial Methyl Proteome in Saccharomyces cerevisiae using Heavy Methyl SILAC. J Proteome Res 2016; 15:4436-4451. [PMID: 27696855 DOI: 10.1021/acs.jproteome.6b00521] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Methylation is a common and abundant post-translational modification. High-throughput proteomic investigations have reported many methylation sites from complex mixtures of proteins. The lack of consistency between parallel studies, resulting from both false positives and missed identifications, suggests problems with both over-reporting and under-reporting methylation sites. However, isotope labeling can be used effectively to address the issue of false-positives, and fractionation of proteins can increase the probability of identifying methylation sites in lower abundance. Here we have adapted heavy methyl SILAC to analyze fractions of the budding yeast Saccharomyces cerevisiae under respiratory conditions to allow for the production of mitochondria, an organelle whose proteins are often overlooked in larger methyl proteome studies. We have found 12 methylation sites on 11 mitochondrial proteins as well as an additional 14 methylation sites on 9 proteins that are nonmitochondrial. Of these methylation sites, 20 sites have not been previously reported. This study represents the first characterization of the yeast mitochondrial methyl proteome and the second proteomic investigation of global mitochondrial methylation to date in any organism.
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Affiliation(s)
- Katelyn E Caslavka Zempel
- Department of Chemistry and Biochemistry and the Molecular Biology Institute and ‡Department of Biological Chemistry and the David Geffen School of Medicine, UCLA , Los Angeles, California 90095, United States
| | - Ajay A Vashisht
- Department of Chemistry and Biochemistry and the Molecular Biology Institute and ‡Department of Biological Chemistry and the David Geffen School of Medicine, UCLA , Los Angeles, California 90095, United States
| | - William D Barshop
- Department of Chemistry and Biochemistry and the Molecular Biology Institute and ‡Department of Biological Chemistry and the David Geffen School of Medicine, UCLA , Los Angeles, California 90095, United States
| | - James A Wohlschlegel
- Department of Chemistry and Biochemistry and the Molecular Biology Institute and ‡Department of Biological Chemistry and the David Geffen School of Medicine, UCLA , Los Angeles, California 90095, United States
| | - Steven G Clarke
- Department of Chemistry and Biochemistry and the Molecular Biology Institute and ‡Department of Biological Chemistry and the David Geffen School of Medicine, UCLA , Los Angeles, California 90095, United States
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11
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Nyakundi DO, Vuko LAM, Bentley SJ, Hoppe H, Blatch GL, Boshoff A. Plasmodium falciparum Hep1 Is Required to Prevent the Self Aggregation of PfHsp70-3. PLoS One 2016; 11:e0156446. [PMID: 27253881 PMCID: PMC4890766 DOI: 10.1371/journal.pone.0156446] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 05/14/2016] [Indexed: 11/29/2022] Open
Abstract
The majority of mitochondrial proteins are encoded in the nucleus and need to be imported from the cytosol into the mitochondria, and molecular chaperones play a key role in the efficient translocation and proper folding of these proteins in the matrix. One such molecular chaperone is the eukaryotic mitochondrial heat shock protein 70 (Hsp70); however, it is prone to self-aggregation and requires the presence of an essential zinc-finger protein, Hsp70-escort protein 1 (Hep1), to maintain its structure and function. PfHsp70-3, the only Hsp70 predicted to localize in the mitochondria of P. falciparum, may also rely on a Hep1 orthologue to prevent self-aggregation. In this study, we identified a putative Hep1 orthologue in P. falciparum and co-expression of PfHsp70-3 and PfHep1 enhanced the solubility of PfHsp70-3. PfHep1 suppressed the thermally induced aggregation of PfHsp70-3 but not the aggregation of malate dehydrogenase or citrate synthase, thus showing specificity for PfHsp70-3. Zinc ions were indeed essential for maintaining the function of PfHep1, as EDTA chelation abrogated its abilities to suppress the aggregation of PfHsp70-3. Soluble and functional PfHsp70-3, acquired by co-expression with PfHep-1, will facilitate the biochemical characterisation of this particular Hsp70 protein and its evaluation as a drug target for the treatment of malaria.
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Affiliation(s)
- David O. Nyakundi
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
| | - Loyiso A. M. Vuko
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
| | - Stephen J. Bentley
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
| | - Heinrich Hoppe
- Department of Biochemistry and Microbiology, Rhodes University, Grahamstown 6140, South Africa
| | - Gregory L. Blatch
- Biomedical Biotechnology Research Unit, Department of Biochemistry and Microbiology, Rhodes University, Grahamstown, South Africa
- College of Health and Biomedicine, Victoria University, Melbourne, Victoria 8001, Australia
| | - Aileen Boshoff
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
- * E-mail:
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12
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Mitochondrial heat shock protein machinery hsp70/hsp40 is indispensable for proper mitochondrial DNA maintenance and replication. mBio 2015; 6:mBio.02425-14. [PMID: 25670781 PMCID: PMC4337576 DOI: 10.1128/mbio.02425-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial chaperones have multiple functions that are essential for proper functioning of mitochondria. In the human-pathogenic protist Trypanosoma brucei, we demonstrate a novel function of the highly conserved machinery composed of mitochondrial heat shock proteins 70 and 40 (mtHsp70/mtHsp40) and the ATP exchange factor Mge1. The mitochondrial DNA of T. brucei, also known as kinetoplast DNA (kDNA), is represented by a single catenated network composed of thousands of minicircles and dozens of maxicircles packed into an electron-dense kDNA disk. The chaperones mtHsp70 and mtHsp40 and their cofactor Mge1 are uniformly distributed throughout the single mitochondrial network and are all essential for the parasite. Following RNA interference (RNAi)-mediated depletion of each of these proteins, the kDNA network shrinks and eventually disappears. Ultrastructural analysis of cells depleted for mtHsp70 or mtHsp40 revealed that the otherwise compact kDNA network becomes severely compromised, a consequence of decreased maxicircle and minicircle copy numbers. Moreover, we show that the replication of minicircles is impaired, although the lack of these proteins has a bigger impact on the less abundant maxicircles. We provide additional evidence that these chaperones are indispensable for the maintenance and replication of kDNA, in addition to their already known functions in Fe-S cluster synthesis and protein import. Impairment or loss of mitochondrial DNA is associated with mitochondrial dysfunction and a wide range of neural, muscular, and other diseases. We present the first evidence showing that the entire mtHsp70/mtHsp40 machinery plays an important role in mitochondrial DNA replication and maintenance, a function likely retained from prokaryotes. These abundant, ubiquitous, and multifunctional chaperones share phenotypes with enzymes engaged in the initial stages of replication of the mitochondrial DNA in T. brucei.
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13
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Týč J, Klingbeil MM, Lukeš J. Mitochondrial heat shock protein machinery hsp70/hsp40 is indispensable for proper mitochondrial DNA maintenance and replication. mBio 2015. [PMID: 25670781 DOI: 10.1128/mbio.02425-02414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2023] Open
Abstract
UNLABELLED Mitochondrial chaperones have multiple functions that are essential for proper functioning of mitochondria. In the human-pathogenic protist Trypanosoma brucei, we demonstrate a novel function of the highly conserved machinery composed of mitochondrial heat shock proteins 70 and 40 (mtHsp70/mtHsp40) and the ATP exchange factor Mge1. The mitochondrial DNA of T. brucei, also known as kinetoplast DNA (kDNA), is represented by a single catenated network composed of thousands of minicircles and dozens of maxicircles packed into an electron-dense kDNA disk. The chaperones mtHsp70 and mtHsp40 and their cofactor Mge1 are uniformly distributed throughout the single mitochondrial network and are all essential for the parasite. Following RNA interference (RNAi)-mediated depletion of each of these proteins, the kDNA network shrinks and eventually disappears. Ultrastructural analysis of cells depleted for mtHsp70 or mtHsp40 revealed that the otherwise compact kDNA network becomes severely compromised, a consequence of decreased maxicircle and minicircle copy numbers. Moreover, we show that the replication of minicircles is impaired, although the lack of these proteins has a bigger impact on the less abundant maxicircles. We provide additional evidence that these chaperones are indispensable for the maintenance and replication of kDNA, in addition to their already known functions in Fe-S cluster synthesis and protein import. IMPORTANCE Impairment or loss of mitochondrial DNA is associated with mitochondrial dysfunction and a wide range of neural, muscular, and other diseases. We present the first evidence showing that the entire mtHsp70/mtHsp40 machinery plays an important role in mitochondrial DNA replication and maintenance, a function likely retained from prokaryotes. These abundant, ubiquitous, and multifunctional chaperones share phenotypes with enzymes engaged in the initial stages of replication of the mitochondrial DNA in T. brucei.
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Affiliation(s)
- Jiří Týč
- Faculty of Sciences, University of South Bohemia and Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
| | - Michele M Klingbeil
- Department of Microbiology, Morrill Science Center, University of Massachusetts, Amherst, Massachusetts, USA
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14
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Lukeš J, Basu S. Fe/S protein biogenesis in trypanosomes - A review. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:1481-92. [PMID: 25196712 DOI: 10.1016/j.bbamcr.2014.08.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 08/25/2014] [Accepted: 08/29/2014] [Indexed: 12/15/2022]
Abstract
Trypanosoma brucei, the causative agent of the African sleeping sickness of humans, and other kinetoplastid flagellates belong to the eukarytotic supergroup Excavata. This early-branching model protist is known for a broad range of unique features. As it is amenable to most techniques of forward and reverse genetics, T. brucei was subject to several studies of its iron-sulfur (Fe/S) protein biogenesis and thus represents the best studied excavate eukaryote. Here we review what is known about the Fe/S protein biogenesis of T. brucei, and focus especially on the comparative and evolutionary interesting aspects. We also explore the connections between the well-known and quite conserved ISC and CIA machineries and the tRNA thiolation pathway. Moreover, the Fe/S cluster protein biogenesis is dissected in the procyclic stage of T. brucei which has an active mitochondrion, as well as in its pathogenic bloodstream stage with a metabolically repressed organelle. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.
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Affiliation(s)
- Julius Lukeš
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences and Faculty of Science, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic.
| | - Somsuvro Basu
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences and Faculty of Science, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic
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15
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Kominek J, Marszalek J, Neuvéglise C, Craig EA, Williams BL. The complex evolutionary dynamics of Hsp70s: a genomic and functional perspective. Genome Biol Evol 2014; 5:2460-77. [PMID: 24277689 PMCID: PMC3879978 DOI: 10.1093/gbe/evt192] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Hsp70 molecular chaperones are ubiquitous. By preventing aggregation, promoting folding, and regulating degradation, Hsp70s are major factors in the ability of cells to maintain proteostasis. Despite a wealth of functional information, little is understood about the evolutionary dynamics of Hsp70s. We undertook an analysis of Hsp70s in the fungal clade Ascomycota. Using the well-characterized 14 Hsp70s of Saccharomyces cerevisiae, we identified 491 orthologs from 53 genomes. Saccharomyces cerevisiae Hsp70s fall into seven subfamilies: four canonical-type Hsp70 chaperones (SSA, SSB, KAR, and SSC) and three atypical Hsp70s (SSE, SSZ, and LHS) that play regulatory roles, modulating the activity of canonical Hsp70 partners. Each of the 53 surveyed genomes harbored at least one member of each subfamily, and thus establishing these seven Hsp70s as units of function and evolution. Genomes of some species contained only one member of each subfamily that is only seven Hsp70s. Overall, members of each subfamily formed a monophyletic group, suggesting that each diversified from their corresponding ancestral gene present in the common ancestor of all surveyed species. However, the pattern of evolution varied across subfamilies. At one extreme, members of the SSB subfamily evolved under concerted evolution. At the other extreme, SSA and SSC subfamilies exhibited a high degree of copy number dynamics, consistent with a birth–death mode of evolution. KAR, SSE, SSZ, and LHS subfamilies evolved in a simple divergent mode with little copy number dynamics. Together, our data revealed that the evolutionary history of this highly conserved and ubiquitous protein family was surprising complex and dynamic.
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Affiliation(s)
- Jacek Kominek
- Laboratory of Evolutionary Biochemistry, Intercollegiate Faculty of Biotechnology, University of Gdansk, Kladki, Poland
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Biology of the heat shock response and protein chaperones: budding yeast (Saccharomyces cerevisiae) as a model system. Microbiol Mol Biol Rev 2012; 76:115-58. [PMID: 22688810 DOI: 10.1128/mmbr.05018-11] [Citation(s) in RCA: 372] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The eukaryotic heat shock response is an ancient and highly conserved transcriptional program that results in the immediate synthesis of a battery of cytoprotective genes in the presence of thermal and other environmental stresses. Many of these genes encode molecular chaperones, powerful protein remodelers with the capacity to shield, fold, or unfold substrates in a context-dependent manner. The budding yeast Saccharomyces cerevisiae continues to be an invaluable model for driving the discovery of regulatory features of this fundamental stress response. In addition, budding yeast has been an outstanding model system to elucidate the cell biology of protein chaperones and their organization into functional networks. In this review, we evaluate our understanding of the multifaceted response to heat shock. In addition, the chaperone complement of the cytosol is compared to those of mitochondria and the endoplasmic reticulum, organelles with their own unique protein homeostasis milieus. Finally, we examine recent advances in the understanding of the roles of protein chaperones and the heat shock response in pathogenic fungi, which is being accelerated by the wealth of information gained for budding yeast.
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Iosefson O, Sharon S, Goloubinoff P, Azem A. Reactivation of protein aggregates by mortalin and Tid1--the human mitochondrial Hsp70 chaperone system. Cell Stress Chaperones 2012; 17:57-66. [PMID: 21811887 PMCID: PMC3227851 DOI: 10.1007/s12192-011-0285-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/05/2011] [Accepted: 07/13/2011] [Indexed: 11/28/2022] Open
Abstract
The mitochondrial 70-kDa heat shock protein (mtHsp70), also known in humans as mortalin, is a central component of the mitochondrial protein import motor and plays a key role in the folding of matrix-localized mitochondrial proteins. MtHsp70 is assisted by a member of the 40-kDa heat shock protein co-chaperone family named Tid1 and a nucleotide exchange factor. Whereas, yeast mtHsp70 has been extensively studied in the context of protein import in the mitochondria, and the bacterial 70-kDa heat shock protein was recently shown to act as an ATP-fuelled unfolding enzyme capable of detoxifying stably misfolded polypeptides into harmless natively refolded proteins, little is known about the molecular functions of the human mortalin in protein homeostasis. Here, we developed novel and efficient purification protocols for mortalin and the two spliced versions of Tid1, Tid1-S, and Tid1-L and showed that mortalin can mediate the in vitro ATP-dependent reactivation of stable-preformed heat-denatured model aggregates, with the assistance of Mge1 and either Tid1-L or Tid1-S co-chaperones or yeast Mdj1. Thus, in addition of being a central component of the protein import machinery, human mortalin together with Tid1, may serve as a protein disaggregating machine which, for lack of Hsp100/ClpB disaggregating co-chaperones, may carry alone the scavenging of toxic protein aggregates in stressed, diseased, or aging human mitochondria.
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Affiliation(s)
- Ohad Iosefson
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978 Israel
| | - Shelly Sharon
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978 Israel
| | - Pierre Goloubinoff
- Département de Biologie Moléculaire Végétale, Université de Lausanne, 1015 Lausanne, Switzerland
| | - Abdussalam Azem
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978 Israel
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18
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Abstract
A common need for microbial cells is the ability to respond to potentially toxic environmental insults. Here we review the progress in understanding the response of the yeast Saccharomyces cerevisiae to two important environmental stresses: heat shock and oxidative stress. Both of these stresses are fundamental challenges that microbes of all types will experience. The study of these environmental stress responses in S. cerevisiae has illuminated many of the features now viewed as central to our understanding of eukaryotic cell biology. Transcriptional activation plays an important role in driving the multifaceted reaction to elevated temperature and levels of reactive oxygen species. Advances provided by the development of whole genome analyses have led to an appreciation of the global reorganization of gene expression and its integration between different stress regimens. While the precise nature of the signal eliciting the heat shock response remains elusive, recent progress in the understanding of induction of the oxidative stress response is summarized here. Although these stress conditions represent ancient challenges to S. cerevisiae and other microbes, much remains to be learned about the mechanisms dedicated to dealing with these environmental parameters.
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Pareek G, Samaddar M, D'Silva P. Primary sequence that determines the functional overlap between mitochondrial heat shock protein 70 Ssc1 and Ssc3 of Saccharomyces cerevisiae. J Biol Chem 2011; 286:19001-13. [PMID: 21474445 PMCID: PMC3099715 DOI: 10.1074/jbc.m110.197434] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The evolutionary diversity of the HSP70 gene family at the genetic level has generated complex structural variations leading to altered functional specificity and mode of regulation in different cellular compartments. By utilizing Saccharomyces cerevisiae as a model system for better understanding the global functional cooperativity between Hsp70 paralogs, we have dissected the differences in functional properties at the biochemical level between mitochondrial heat shock protein 70 (mtHsp70) Ssc1 and an uncharacterized Ssc3 paralog. Based on the evolutionary origin of Ssc3 and a high degree of sequence homology with Ssc1, it has been proposed that both have a close functional overlap in the mitochondrial matrix. Surprisingly, our results demonstrate that there is no functional cross-talk between Ssc1 and Ssc3 paralogs. The lack of in vivo functional overlap is due to altered conformation and significant lower stability associated with Ssc3. The substrate-binding domain of Ssc3 showed poor affinity toward mitochondrial client proteins and Tim44 due to the open conformation in ADP-bound state. In addition to that, the nucleotide-binding domain of Ssc3 showed an altered regulation by the Mge1 co-chaperone due to a high degree of conformational plasticity, which strongly promotes aggregation. Besides, Ssc3 possesses a dysfunctional inter-domain interface thus rendering it unable to perform functions similar to generic Hsp70s. Moreover, we have identified the critical amino acid sequence of Ssc1 and Ssc3 that can "make or break" mtHsp70 chaperone function. Together, our analysis provides the first evidence to show that the nucleotide-binding domain of mtHsp70s plays a critical role in determining the functional specificity among paralogs and orthologs across kingdoms.
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Affiliation(s)
- Gautam Pareek
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
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20
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Mapa K, Sikor M, Kudryavtsev V, Waegemann K, Kalinin S, Seidel CAM, Neupert W, Lamb DC, Mokranjac D. The conformational dynamics of the mitochondrial Hsp70 chaperone. Mol Cell 2010; 38:89-100. [PMID: 20385092 DOI: 10.1016/j.molcel.2010.03.010] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2009] [Revised: 02/03/2010] [Accepted: 03/22/2010] [Indexed: 12/31/2022]
Abstract
Heat shock proteins 70 (Hsp70) represent a ubiquitous and conserved family of molecular chaperones involved in a plethora of cellular processes. The dynamics of their ATP hydrolysis-driven and cochaperone-regulated conformational cycle are poorly understood. We used fluorescence spectroscopy to analyze, in real time and at single-molecule resolution, the effects of nucleotides and cochaperones on the conformation of Ssc1, a mitochondrial member of the family. We report that the conformation of its ADP state is unexpectedly heterogeneous, in contrast to a uniform ATP state. Substrates are actively involved in determining the conformation of Ssc1. The J protein Mdj1 does not interact transiently with the chaperone, as generally believed, but rather is released slowly upon ATP hydrolysis. Analysis of the major bacterial Hsp70 revealed important differences between highly homologous members of the family, possibly explaining tuning of Hsp70 chaperones to meet specific functions in different organisms and cellular compartments.
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Affiliation(s)
- Koyeli Mapa
- Institute for Physiological Chemistry, LMU München, 81377 Munich, Germany
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21
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Goswami AV, Chittoor B, D'Silva P. Understanding the functional interplay between mammalian mitochondrial Hsp70 chaperone machine components. J Biol Chem 2010; 285:19472-82. [PMID: 20392697 PMCID: PMC2885226 DOI: 10.1074/jbc.m110.105957] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria biogenesis requires the import of several precursor proteins that are synthesized in the cytosol. The mitochondrial heat shock protein 70 (mtHsp70) machinery components are highly conserved among eukaryotes, including humans. However, the functional properties of human mtHsp70 machinery components have not been characterized among all eukaryotic families. To study the functional interactions, we have reconstituted the components of the mtHsp70 chaperone machine (Hsp70/J-protein/GrpE/Hep) and systematically analyzed in vitro conditions for biochemical functions. We observed that the sequence-specific interaction of human mtHsp70 toward mitochondrial client proteins differs significantly from its yeast counterpart Ssc1. Interestingly, the helical lid of human mtHsp70 was found dispensable to the binding of P5 peptide as compared with the other Hsp70s. We observed that the two human mitochondrial matrix J-protein splice variants differentially regulate the mtHsp70 chaperone cycle. Strikingly, our results demonstrated that human Hsp70 escort protein (Hep) possesses a unique ability to stimulate the ATPase activity of mtHsp70 as well as to prevent the aggregation of unfolded client proteins similar to J-proteins. We observed that Hep binds with the C terminus of mtHsp70 in a full-length context and this interaction is distinctly different from unfolded client-specific or J-protein binding. In addition, we found that the interaction of Hep at the C terminus of mtHsp70 is regulated by the helical lid region. However, the interaction of Hep at the ATPase domain of the human mtHsp70 is mutually exclusive with J-proteins, thus promoting a similar conformational change that leads to ATPase stimulation. Additionally, we highlight the biochemical defects of the mtHsp70 mutant (G489E) associated with a myelodysplastic syndrome.
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Affiliation(s)
- Arvind Vittal Goswami
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
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22
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Blamowska M, Sichting M, Mapa K, Mokranjac D, Neupert W, Hell K. ATPase domain and interdomain linker play a key role in aggregation of mitochondrial Hsp70 chaperone Ssc1. J Biol Chem 2009; 285:4423-31. [PMID: 20007714 DOI: 10.1074/jbc.m109.061697] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The co-chaperone Hep1 is required to prevent the aggregation of mitochondrial Hsp70 proteins. We have analyzed the interaction of Hep1 with mitochondrial Hsp70 (Ssc1) and the determinants in Ssc1 that make it prone to aggregation. The ATPase and peptide binding domain (PBD) of Hsp70 proteins are connected by a linker segment that mediates interdomain communication between the domains. We show here that the minimal Hep1 binding entity of Ssc1 consists of the ATPase domain and the interdomain linker. In the absence of Hep1, the ATPase domain with the interdomain linker had the tendency to aggregate, in contrast to the ATPase domain with the mutated linker segment or without linker, and in contrast to the PBD. The closest homolog of Ssc1, bacterial DnaK, and a Ssc1 chimera, in which a segment of the ATPase domain of Ssc1 was replaced by the corresponding segment from DnaK, did not aggregate in Delta hep1 mitochondria. The propensity to aggregate appears to be a specific property of the mitochondrial Hsp70 proteins. The ATPase domain in combination with the interdomain linker is crucial for aggregation of Ssc1. In conclusion, our results suggest that interdomain communication makes Ssc1 prone to aggregation. Hep1 counteracts aggregation by binding to this aggregation-prone conformer.
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Affiliation(s)
- Marta Blamowska
- Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5, 81377 München, Germany
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23
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Abstract
Heat-shock proteins (hsps) have been identified as molecular chaperones conserved between microbes and man and grouped by their molecular mass and high degree of amino acid homology. This article reviews the major hsps of Saccharomyces cerevisiae, their interactions with trehalose, the effect of fermentation and the role of the heat-shock factor. Information derived from this model, as well as from Neurospora crassa and Achlya ambisexualis, helps in understanding the importance of hsps in the pathogenic fungi, Candida albicans, Cryptococcus neoformans, Aspergillus spp., Histoplasma capsulatum, Paracoccidioides brasiliensis, Trichophyton rubrum, Phycomyces blakesleeanus, Fusarium oxysporum, Coccidioides immitis and Pneumocystis jiroveci. This has been matched with proteomic and genomic information examining hsp expression in response to noxious stimuli. Fungal hsp90 has been identified as a target for immunotherapy by a genetically recombinant antibody. The concept of combining this antibody fragment with an antifungal drug for treating life-threatening fungal infection and the potential interactions with human and microbial hsp90 and nitric oxide is discussed.
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Affiliation(s)
- James P Burnie
- Department of Medical Microbiology, Clinical Sciences Building, University of Manchester, Manchester Royal Infirmary, Manchester, UK.
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24
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Mokranjac D, Sichting M, Popov-Celeketić D, Berg A, Hell K, Neupert W. The import motor of the yeast mitochondrial TIM23 preprotein translocase contains two different J proteins, Tim14 and Mdj2. J Biol Chem 2005; 280:31608-14. [PMID: 16027163 DOI: 10.1074/jbc.m502397200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The import motor of the mitochondrial (mt)TIM23 complex drives translocation of presequence-containing preproteins across the mitochondrial inner membrane in an ATP-dependent manner. Tim44 is the central component of the motor. It recruits mtHsp70, which binds the incoming preproteins. The J protein Tim14 stimulates the ATPase activity of mtHsp70 and thereby enables efficient binding of mtHsp70 to preproteins. Tim16 is a J-like protein that forms a stable subcomplex with Tim14 and recruits it to the translocase. All subunits of the TIM23 translocase but one are essential for yeast cell viability. Yeast cells contain a close homologue of Tim14, Mdj2. In contrast to Tim14, its deletion leads to no obvious growth defect. In the present study we analyzed Mdj2 and compared it with Tim14. Mdj2 forms a complex with Tim16 and is recruited to the TIM23 translocase. It stimulates the ATPase activity of mtHsp70 to the same extent that Tim14 does. Mdj2 is expressed at a lower level compared with Tim14, and its complex with Tim16 is less stable. However, overexpressed Mdj2 fully restores the growth of cells lacking Tim14. We conclude that Mdj2 is a functional J protein and a component of the mitochondrial import motor.
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Affiliation(s)
- Dejana Mokranjac
- Institut für Physiologische Chemie, Universität München, Butenandtstrasse 5, 81377 München, Germany
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25
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Schwimmer C, Lefebvre-Legendre L, Rak M, Devin A, Slonimski PP, di Rago JP, Rigoulet M. Increasing mitochondrial substrate-level phosphorylation can rescue respiratory growth of an ATP synthase-deficient yeast. J Biol Chem 2005; 280:30751-9. [PMID: 15975925 DOI: 10.1074/jbc.m501831200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In a previous study we have identified Fmc1p, a mitochondrial protein involved in the assembly/stability of the yeast F0F1-ATP synthase at elevated temperatures. The deltafmc1 mutant was shown to exhibit a severe phenotype of very slow growth on respiratory substrates at 37 degrees C. We have isolated ODC1 as a multicopy suppressor of the fmc1 deletion restoring a good respiratory growth. Odc1p expression level was estimated to be at least 10 times higher in mitochondria isolated from the deltafmc1/ODC1 transformant as compared with wild type mitochondria. Interestingly, ODC1 encodes an oxodicarboxylate carrier, which transports alpha-ketoglutarate and alpha-ketoadipate or any other transported tricarboxylic acid cycle intermediate in a counter-exchange through the inner mitochondrial membrane. We show that the suppression of the respiratory-growth-deficient fmc1 by the overexpressed Odc1p was not due to a restored stable ATP synthase. Instead, the rescuing mechanism involves an increase in the flux of tricarboxylic acid cycle intermediate from the cytosol into the mitochondria, leading to an increase in the alpha-ketoglutarate oxidative decarboxylation, resulting in an increase in mitochondrial substrate-level-dependent ATP synthesis. This mechanism of metabolic bypass of a defective ATP synthase unravels the physiological importance of intramitochondrial substrate-level phosphorylations. This unexpected result might be of interest for the development of therapeutic solutions in pathologies associated with defects in the oxidative phosphorylation system.
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Affiliation(s)
- Christine Schwimmer
- Institut de Biochimie et Génétique Cellulaires CNRS/Université Victor Ségalen Bordeaux2, 1 rue Camille St Saëns, 33077 Bordeaux Cedex, France.
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26
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Sichting M, Mokranjac D, Azem A, Neupert W, Hell K. Maintenance of structure and function of mitochondrial Hsp70 chaperones requires the chaperone Hep1. EMBO J 2005; 24:1046-56. [PMID: 15719019 PMCID: PMC554129 DOI: 10.1038/sj.emboj.7600580] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Accepted: 01/20/2005] [Indexed: 11/08/2022] Open
Abstract
Hsp70 chaperones mediate folding of proteins and prevent their misfolding and aggregation. We report here on a new kind of Hsp70 interacting protein in mitochondria, Hep1. Hep1 is a highly conserved protein present in virtually all eukaryotes. Deletion of HEP1 results in a severe growth defect. Cells lacking Hep1 are deficient in processes that need the function of mitochondrial Hsp70s, such as preprotein import and biogenesis of proteins containing FeS clusters. In the mitochondria of these cells, Hsp70s, Ssc1 and Ssq1 accumulate as insoluble aggregates. We show that it is the nucleotide-free form of mtHsp70 that has a high tendency to self-aggregate. This process is efficiently counteracted by Hep1. We conclude that Hep1 acts as a chaperone that is necessary and sufficient to prevent self-aggregation and to thereby maintain the function of the mitochondrial Hsp70 chaperones.
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Affiliation(s)
- Martin Sichting
- Adolf-Butenandt-Institut, Lehrstuhl für Physiologische Chemie, Ludwig-Maximilians-Universität München, München, Germany
| | - Dejana Mokranjac
- Adolf-Butenandt-Institut, Lehrstuhl für Physiologische Chemie, Ludwig-Maximilians-Universität München, München, Germany
| | - Abdussalam Azem
- Department of Biochemistry, Tel-Aviv University, Tel-Aviv, Israel
| | - Walter Neupert
- Adolf-Butenandt-Institut, Lehrstuhl für Physiologische Chemie, Ludwig-Maximilians-Universität München, München, Germany
- Adolf-Butenandt-Institut, Lehrstuhl für Physiologische Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5, 81377 München, Germany. Tel.: +49 89 2180 77095; Fax: +49 89 2180 77093; E-mail:
| | - Kai Hell
- Adolf-Butenandt-Institut, Lehrstuhl für Physiologische Chemie, Ludwig-Maximilians-Universität München, München, Germany
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27
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Sakasegawa Y, Hachiya NS, Tsukita S, Kaneko K. Ecm10p localizes in yeast mitochondrial nucleoids and its overexpression induces extensive mitochondrial DNA aggregations. Biochem Biophys Res Commun 2003; 309:217-21. [PMID: 12943685 DOI: 10.1016/s0006-291x(03)01548-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ecm10p was initially identified as a cell wall synthesis-related gene product [Genetics 147 (1997) 435] and also reported as a mitochondrial protein which was partially capable of compensating the phenotypic defect by SSC1 gene mutation [FEBS Lett. 487 (2000) 307]. Here we report that ecm10p is localized in mitochondrial nucleoids as its major component and the targeting signal resides between amino acid residues 161 and 240. Overexpression of ecm10p induces extensive mitochondrial DNA aggregations, which might be due to aberrant mitochondrial DNA cleavages through an altered endonuclease activity in mitochondrial nucleoids.
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Affiliation(s)
- Yuji Sakasegawa
- Department of Cortical Function Disorders, National Institute of Neuroscience (NIN), National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi Kodaira, Tokyo, Japan
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28
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Cabiscol E, Bellí G, Tamarit J, Echave P, Herrero E, Ros J. Mitochondrial Hsp60, resistance to oxidative stress, and the labile iron pool are closely connected in Saccharomyces cerevisiae. J Biol Chem 2002; 277:44531-8. [PMID: 12200437 DOI: 10.1074/jbc.m206525200] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the present study, we have analyzed the role of the molecular chaperone Hsp60 in protection of Saccharomyces cerevisiae against oxidative damage. We constructed mutant strains in which the levels of Hsp60 protein, compared with wild-type cells, were four times greater, and the addition of doxycycline gradually reduces them to 20% of wild-type. Under oxidative-stress conditions, the progressive decrease in Hsp60 levels in these mutants resulted in reduced cell viability and an increase in both cell peroxide species and protein carbonyl content. Protection of Fe/S-containing enzymes from oxidative inactivation was found to be dose-dependent with respect to Hsp60 levels. As these enzymes release their iron ions under oxidative-stress conditions, the intracellular labile iron pool, monitored with calcein, was higher in cells with reduced Hsp60 levels. Consistently, the iron chelator deferoxamine protected low Hsp60-expressing cells from both oxidant-induced death and protein oxidation. These results indicate that the role of Hsp60 in oxidative-stress defense is explained by protection of several Fe/S proteins, which prevent the release of iron ions and thereby avert further damage.
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Affiliation(s)
- Elisa Cabiscol
- Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina, Universitat de Lleida, Spain
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29
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Voos W, Röttgers K. Molecular chaperones as essential mediators of mitochondrial biogenesis. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1592:51-62. [PMID: 12191768 DOI: 10.1016/s0167-4889(02)00264-1] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Chaperone proteins have been initially identified by their ability to confer cellular resistance to various stress conditions. However, molecular chaperones participate also in many constitutive cellular processes. Mitochondria contain several members of the major chaperone families that have important functions in maintaining mitochondrial function. The major Hsp70 of the mitochondrial matrix (mtHsp70) is essential for the translocation of cytosolic precursor proteins across the two mitochondrial membranes. MtHsp70 interacts with the preprotein in transit in an ATP-dependent reaction as it emerges from the translocation channel of the inner membrane. Together with two essential partner proteins, Tim44 and Mge1, mtHsp70 forms a membrane-associated import motor complex responsible for vectorial polypeptide movement and unfolding of preprotein domains. Folding of newly imported proteins in the matrix is assisted by the soluble chaperone system formed by mtHsp70 and its partner protein Mdj1. For certain substrate proteins, the protected folding environment that is offered by the large oligomeric Hsp60 complex facilitates further folding reactions. The mitochondrial Hsp70 Ssq1 is involved in the assembly of mitochondrial Fe/S clusters together with another member of the DnaJ family, Jac1. Chaperones of the Clp/Hsp100 family mediate the prevention of aggregation under stress conditions and eventually the degradation of mitochondrial proteins. Together, the chaperones of the mitochondrial matrix form a complex interdependent chaperone network that is essential for most reactions of mitochondrial protein biogenesis.
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Affiliation(s)
- Wolfgang Voos
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Str. 7, D-79104, Freiburg, Germany.
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30
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Strub A, Röttgers K, Voos W. The Hsp70 peptide-binding domain determines the interaction of the ATPase domain with Tim44 in mitochondria. EMBO J 2002; 21:2626-35. [PMID: 12032075 PMCID: PMC126037 DOI: 10.1093/emboj/21.11.2626] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ssc1, a molecular chaperone of the Hsp70 family, drives preprotein import into the mitochondrial matrix by a specific interaction with the translocase component Tim44. Two other mitochondrial Hsp70s, Ssc3 (Ecm10) and Ssq1, show high sequence homology to Ssc1 but fail to replace Ssc1 in vivo, possibly due to their inability to interact with Tim44. We analyzed the structural basis of the Tim44 interaction by the construction of chimeric Hsp70 proteins. The ATPase domains of all three mitochondrial Hsp70s were shown to bind to Tim44, supporting the active motor model for the Hsp70 mechanism during preprotein translocation. The peptide-binding domain of Ssc1 sustained binding of Tim44, while the peptide-binding domains of Ssc3 and Ssq1 exerted a negative effect on the interaction of the ATPase domains with Tim44. A mutation in the peptide-binding domain of Ssc1 resulted in a similar negative effect not only on the ATPase domain of Ssc1, but also of Ssq1 and Ssc3. Hence, the determination of a crucial Hsp70 function via the peptide-binding domain suggests a new regulatory principle for Hsp70 domain cooperation.
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Affiliation(s)
- Andreas Strub
- Institut für Biochemie und Molekularbiologie, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany
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31
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Schmidt S, Strub A, Röttgers K, Zufall N, Voos W. The two mitochondrial heat shock proteins 70, Ssc1 and Ssq1, compete for the cochaperone Mge1. J Mol Biol 2001; 313:13-26. [PMID: 11601843 DOI: 10.1006/jmbi.2001.5013] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two members of the heat shock protein 70 kDa (Hsp70) family, Ssc1 and Ssq1, perform important functions in the mitochondrial matrix. The essential Ssc1 is an abundant ATP-binding protein required for both import and folding of mitochondrial proteins. The function of Ssc1 is supported by an interaction with the preprotein translocase subunit Tim44, the cochaperone Mdj1, and the nucleotide exchange factor Mge1. In contrast, only limited information is available on Ssq1. So far, a basic characterization of Ssq1 has demonstrated its involvement in the maintenance of mitochondrial DNA, the maturation of the yeast frataxin (Yfh1) after import, and assembly of the mitochondrial Fe/S cluster. Here, we analyzed the biochemical properties and the interaction partners of Ssq1 in detail. Ssq1 showed typical chaperone properties by binding to unfolded substrate proteins in an ATP-regulated manner. Ssq1 was able to form a specific complex with the nucleotide exchange factor Mge1. In particular, complex formation in organello was enhanced significantly when Ssc1 was inactivated selectively. However, even under these conditions, no interaction of Ssq1 with the two other mitochondrial Hsp70-cochaperones, Tim44 and Mdj1, was observed. The Ssq1-Mge1 interaction showed a lower overall stability but the same characteristic nucleotide-dependence as the Ssc1-Mge1 interaction. A quantitative analysis of the interaction properties indicated a competition of Ssq1 with Ssc1 for binding to Mge1. Perturbation of Mge1 function or amounts resulted in direct effects on Ssq1 activity in intact mitochondria. We conclude that mitochondria represent the unique case where two Hsp70s compete for the interaction with one nucleotide exchange factor.
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Affiliation(s)
- S Schmidt
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Str. 7, D-79104, Germany
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Lutz T, Westermann B, Neupert W, Herrmann JM. The mitochondrial proteins Ssq1 and Jac1 are required for the assembly of iron sulfur clusters in mitochondria. J Mol Biol 2001; 307:815-25. [PMID: 11273703 DOI: 10.1006/jmbi.2001.4527] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondria of the yeast Saccharomyces cerevisiae contain three different Hsp70 chaperones, Ssc1, Ecm10 and Ssq1. Ssc1 is an essential protein that mediates the import of nuclear-encoded proteins into the organelle and their subsequent folding. The nucleotide state of Ssc1 is thereby regulated by the nucleotide exchange factor Mge1. Here, we show that Mge1 interacts with Ssq1 in an ATP-dependent manner, suggesting that Mge1 also regulates Ssq1 function. In contrast to Ssc1, Ssq1 does not associate with the Tim44 subunit of the protein translocating complex, indicating a different function of both chaperones. Mutants in Ssq1 were reported to have low levels of iron sulfur (FeS) cluster-containing enzymes. Employing an assay that allowed us to monitor the conversion of the apoform of mitochondrial ferredoxin into its FeS-containing holoform, Ssq1 was demonstrated to be required for the FeS cluster assembly in mitochondria. The mitochondrial DnaJ homolog Jac1 is crucial for this process, whereas Mdj1 function is dispensable. Furthermore, the presence of frataxin is necessary for FeS cluster assembly into ferredoxin suggesting a role for frataxin at the level of the formation of holo-ferredoxin.
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Affiliation(s)
- T Lutz
- Institut für Physiologische, Chemie der Universität München, Goethestrasse 33, München, 80336, Germany
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Current Awareness. Yeast 2001. [DOI: 10.1002/yea.685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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