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Costa MD, Maciel P. Modifier pathways in polyglutamine (PolyQ) diseases: from genetic screens to drug targets. Cell Mol Life Sci 2022; 79:274. [PMID: 35503478 PMCID: PMC11071829 DOI: 10.1007/s00018-022-04280-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 03/14/2022] [Accepted: 03/30/2022] [Indexed: 12/17/2022]
Abstract
Polyglutamine (PolyQ) diseases include a group of inherited neurodegenerative disorders caused by unstable expansions of CAG trinucleotide repeats in the coding region of specific genes. Such genetic alterations produce abnormal proteins containing an unusually long PolyQ tract that renders them more prone to aggregate and cause toxicity. Although research in the field in the last years has contributed significantly to the knowledge of the biological mechanisms implicated in these diseases, effective treatments are still lacking. In this review, we revisit work performed in models of PolyQ diseases, namely the yeast Saccharomyces cerevisiae, the nematode worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster, and provide a critical overview of the high-throughput unbiased genetic screens that have been performed using these systems to identify novel genetic modifiers of PolyQ diseases. These approaches have revealed a wide variety of cellular processes that modulate the toxicity and aggregation of mutant PolyQ proteins, reflecting the complexity of these disorders and demonstrating how challenging the development of therapeutic strategies can be. In addition to the unbiased large-scale genetic screenings in non-vertebrate models, complementary studies in mammalian systems, closer to humans, have contributed with novel genetic modifiers of PolyQ diseases, revealing neuronal function and inflammation as key disease modulators. A pathway enrichment analysis, using the human orthologues of genetic modifiers of PolyQ diseases clustered modifier genes into major themes translatable to the human disease context, such as protein folding and transport as well as transcription regulation. Innovative genetic strategies of genetic manipulation, together with significant advances in genomics and bioinformatics, are taking modifier genetic studies to more realistic disease contexts. The characterization of PolyQ disease modifier pathways is of extreme relevance to reveal novel therapeutic possibilities to delay disease onset and progression in patients.
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Affiliation(s)
- Marta Daniela Costa
- School of Medicine, Life and Health Sciences Research Institute (ICVS), University of Minho, 4710-057, Braga, Portugal
- ICVS/3Bs-PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Patrícia Maciel
- School of Medicine, Life and Health Sciences Research Institute (ICVS), University of Minho, 4710-057, Braga, Portugal.
- ICVS/3Bs-PT Government Associate Laboratory, Braga/Guimarães, Portugal.
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Chernoff YO, Grizel AV, Rubel AA, Zelinsky AA, Chandramowlishwaran P, Chernova TA. Application of yeast to studying amyloid and prion diseases. ADVANCES IN GENETICS 2020; 105:293-380. [PMID: 32560789 PMCID: PMC7527210 DOI: 10.1016/bs.adgen.2020.01.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyloids are fibrous cross-β protein aggregates that are capable of proliferation via nucleated polymerization. Amyloid conformation likely represents an ancient protein fold and is linked to various biological or pathological manifestations. Self-perpetuating amyloid-based protein conformers provide a molecular basis for transmissible (infectious or heritable) protein isoforms, termed prions. Amyloids and prions, as well as other types of misfolded aggregated proteins are associated with a variety of devastating mammalian and human diseases, such as Alzheimer's, Parkinson's and Huntington's diseases, transmissible spongiform encephalopathies (TSEs), amyotrophic lateral sclerosis (ALS) and transthyretinopathies. In yeast and fungi, amyloid-based prions control phenotypically detectable heritable traits. Simplicity of cultivation requirements and availability of powerful genetic approaches makes yeast Saccharomyces cerevisiae an excellent model system for studying molecular and cellular mechanisms governing amyloid formation and propagation. Genetic techniques allowing for the expression of mammalian or human amyloidogenic and prionogenic proteins in yeast enable researchers to capitalize on yeast advantages for characterization of the properties of disease-related proteins. Chimeric constructs employing mammalian and human aggregation-prone proteins or domains, fused to fluorophores or to endogenous yeast proteins allow for cytological or phenotypic detection of disease-related protein aggregation in yeast cells. Yeast systems are amenable to high-throughput screening for antagonists of amyloid formation, propagation and/or toxicity. This review summarizes up to date achievements of yeast assays in application to studying mammalian and human disease-related aggregating proteins, and discusses both limitations and further perspectives of yeast-based strategies.
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Affiliation(s)
- Yury O Chernoff
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States; Laboratory of Amyloid Biology, St. Petersburg State University, St. Petersburg, Russia.
| | - Anastasia V Grizel
- Laboratory of Amyloid Biology, St. Petersburg State University, St. Petersburg, Russia
| | - Aleksandr A Rubel
- Laboratory of Amyloid Biology, St. Petersburg State University, St. Petersburg, Russia; Department of Genetics and Biotechnology, St. Petersburg State University, St. Petersburg, Russia; Sirius University of Science and Technology, Sochi, Russia
| | - Andrew A Zelinsky
- Laboratory of Amyloid Biology, St. Petersburg State University, St. Petersburg, Russia
| | | | - Tatiana A Chernova
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, United States
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Rencus-Lazar S, DeRowe Y, Adsi H, Gazit E, Laor D. Yeast Models for the Study of Amyloid-Associated Disorders and Development of Future Therapy. Front Mol Biosci 2019; 6:15. [PMID: 30968029 PMCID: PMC6439353 DOI: 10.3389/fmolb.2019.00015] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/01/2019] [Indexed: 12/28/2022] Open
Abstract
First described almost two decades ago, the pioneering yeast models of neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's diseases, have become well-established research tools, providing both basic mechanistic insights as well as a platform for the development of therapeutic agents. These maladies are associated with the formation of aggregative amyloid protein structures showing common characteristics, such as the assembly of soluble oligomeric species, binding of indicative dyes, and apoptotic cytotoxicity. The canonical yeast models have recently been expanded by the establishment of a model for type II diabetes, a non-neurological amyloid-associated disease. While these model systems require the exogenous expression of mammalian proteins in yeast, an additional amyloid-associated disease model, comprising solely mutations of endogenous yeast genes, has been recently described. Mutated in the adenine salvage pathway, this yeast model exhibits adenine accumulation, thereby recapitulating adenine inborn error of metabolism disorders. Moreover, in line with the recent extension of the amyloid hypothesis to include metabolite amyloids, in addition to protein-associated ones, the intracellular assembly of adenine amyloid-like structures has been demonstrated using this yeast model. In this review, we describe currently available yeast models of diverse amyloid-associated disorders, as well as their impact on our understanding of disease mechanisms and contribution to future potential drug development.
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Affiliation(s)
- Sigal Rencus-Lazar
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Yasmin DeRowe
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Hanaa Adsi
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ehud Gazit
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.,BLAVATNIK CENTER for Drug Discovery, Tel Aviv University, Tel Aviv, Israel.,Department of Materials Science and Engineering, Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel
| | - Dana Laor
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Tuite MF. Yeast models of neurodegenerative diseases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2019; 168:351-379. [DOI: 10.1016/bs.pmbts.2019.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Natural Genetic Variation in Yeast Reveals That NEDD4 Is a Conserved Modifier of Mutant Polyglutamine Aggregation. G3-GENES GENOMES GENETICS 2018; 8:3421-3431. [PMID: 30194090 PMCID: PMC6222566 DOI: 10.1534/g3.118.200289] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A feature common to late onset proteinopathic disorders is an accumulation of toxic protein conformers and aggregates in affected tissues. In the search for potential drug targets, many studies used high-throughput screens to find genes that modify the cytotoxicity of misfolded proteins. A complement to this approach is to focus on strategies that use protein aggregation as a phenotypic readout to identify pathways that control aggregate formation and maintenance. Here we use natural variation between strains of budding yeast to genetically map loci that influence the aggregation of a polyglutamine-containing protein derived from a mutant form of huntingtin, the causative agent in Huntington disease. Linkage analysis of progeny derived from a cross between wild and laboratory yeast strains revealed two polymorphic loci that modify polyglutamine aggregation. One locus contains the gene RFU1 which modifies ubiquitination states of misfolded proteins targeted by the E3-ubiquitin ligase complex Rsp5 Activity of the Rsp5 complex, and the mammalian homolog NEDD4, are critical in maintaining protein homeostasis in response to proteomic stress. Our analysis also showed linkage of the aggregation phenotype to a distinct locus containing a gene encoding the Rsp5-interacting Bul2 protein. Allele-swap experiments validated the impact of both RFU1 and BUL2 on huntingtin aggregation. Furthermore, we found that the nematode Caenorhabditis elegans' ortholog of Rsp5, wwp-1, also negatively regulates polyglutamine aggregation. Knockdown of the NEDD4 in human cells likewise altered polyglutamine aggregation. Taken together, these results implicate conserved processes involving the ubiquitin regulation network that modify protein aggregation and provide novel therapeutic targets for polyglutamine and other protein folding diseases.
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Hofer S, Kainz K, Zimmermann A, Bauer MA, Pendl T, Poglitsch M, Madeo F, Carmona-Gutierrez D. Studying Huntington's Disease in Yeast: From Mechanisms to Pharmacological Approaches. Front Mol Neurosci 2018; 11:318. [PMID: 30233317 PMCID: PMC6131589 DOI: 10.3389/fnmol.2018.00318] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 08/16/2018] [Indexed: 12/22/2022] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder that leads to progressive neuronal loss, provoking impaired motor control, cognitive decline, and dementia. So far, HD remains incurable, and available drugs are effective only for symptomatic management. HD is caused by a mutant form of the huntingtin protein, which harbors an elongated polyglutamine domain and is highly prone to aggregation. However, many aspects underlying the cytotoxicity of mutant huntingtin (mHTT) remain elusive, hindering the efficient development of applicable interventions to counteract HD. An important strategy to obtain molecular insights into human disorders in general is the use of eukaryotic model organisms, which are easy to genetically manipulate and display a high degree of conservation regarding disease-relevant cellular processes. The budding yeast Saccharomyces cerevisiae has a long-standing and successful history in modeling a plethora of human maladies and has recently emerged as an effective tool to study neurodegenerative disorders, including HD. Here, we summarize some of the most important contributions of yeast to HD research, specifically concerning the elucidation of mechanistic features of mHTT cytotoxicity and the potential of yeast as a platform to screen for pharmacological agents against HD.
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Affiliation(s)
- Sebastian Hofer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Katharina Kainz
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Andreas Zimmermann
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
- Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Maria A. Bauer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Tobias Pendl
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Michael Poglitsch
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Frank Madeo
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
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The RNA-Binding Protein Scp160p Facilitates Aggregation of Many Endogenous Q/N-Rich Proteins. Cell Rep 2018; 24:20-26. [DOI: 10.1016/j.celrep.2018.06.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 04/18/2018] [Accepted: 06/01/2018] [Indexed: 01/05/2023] Open
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Bhattacharyya S, Bershtein S, Yan J, Argun T, Gilson AI, Trauger SA, Shakhnovich EI. Transient protein-protein interactions perturb E. coli metabolome and cause gene dosage toxicity. eLife 2016; 5. [PMID: 27938662 PMCID: PMC5176355 DOI: 10.7554/elife.20309] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 12/09/2016] [Indexed: 12/31/2022] Open
Abstract
Gene dosage toxicity (GDT) is an important factor that determines optimal levels of protein abundances, yet its molecular underpinnings remain unknown. Here, we demonstrate that overexpression of DHFR in E. coli causes a toxic metabolic imbalance triggered by interactions with several functionally related enzymes. Though deleterious in the overexpression regime, surprisingly, these interactions are beneficial at physiological concentrations, implying their functional significance in vivo. Moreover, we found that overexpression of orthologous DHFR proteins had minimal effect on all levels of cellular organization - molecular, systems, and phenotypic, in sharp contrast to E. coli DHFR. Dramatic difference of GDT between 'E. coli's self' and 'foreign' proteins suggests the crucial role of evolutionary selection in shaping protein-protein interaction (PPI) networks at the whole proteome level. This study shows how protein overexpression perturbs a dynamic metabolon of weak yet potentially functional PPI, with consequences for the metabolic state of cells and their fitness.
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Affiliation(s)
- Sanchari Bhattacharyya
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Shimon Bershtein
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Jin Yan
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States.,College of Chemical Engineering, Sichuan University, Chengdu, China
| | - Tijda Argun
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Amy I Gilson
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Sunia A Trauger
- Small Molecule Mass Spectrometry, Northwest Laboratories, Harvard University, Cambridge, United States
| | - Eugene I Shakhnovich
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
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Serpionov GV, Alexandrov AI, Ter-Avanesyan MD. Distinct mechanisms of mutant huntingtin toxicity in different yeast strains. FEMS Yeast Res 2016; 17:fow102. [PMID: 27915242 DOI: 10.1093/femsyr/fow102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 10/17/2016] [Accepted: 12/01/2016] [Indexed: 11/12/2022] Open
Abstract
Expansion of polyglutamine stretches in several proteins causes neurodegenerative amyloidoses, including Huntington disease. In yeast, mutant huntingtin (mHtt) with a stretch of 103 glutamine residues (HttQ103) forms toxic aggregates. A range of yeast strains have been used to elucidate the mechanisms of mHtt toxicity, and have revealed perturbations of various unrelated processes. HttQ103 aggregates can induce aggregation of cellular proteins, many of which contain glutamine/asparagine-rich regions, including Sup35 and Def1. In the strain 74-D694 HttQ103, toxicity is related to aggregation-mediated depletion of soluble Sup35 and its interacting partner Sup45. Def1 was also implicated in mHtt toxicity, since its lack detoxified HttQ103 in another yeast strain, BY4741. Here we show that in BY4742, deletion of DEF1 lowers HttQ103 toxicity and decreases the amount of its polymers, but does not affect copolymerization of Sup35. Furthermore, in contrast to 74-D694, increasing the levels of soluble Sup35 and Sup45 does not alleviate toxicity of HttQ103 in BY4742. These data demonstrate a difference in the mechanisms underlying mHtt toxicity in different yeast strains and suggest that in humans with Huntington disease, neurons of different brain compartments and cells in other tissues can also be damaged by different mechanisms.
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Affiliation(s)
- Genrikh V Serpionov
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
| | - Alexander I Alexandrov
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
| | - Michael D Ter-Avanesyan
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
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10
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Multiple discrete soluble aggregates influence polyglutamine toxicity in a Huntington's disease model system. Sci Rep 2016; 6:34916. [PMID: 27721444 PMCID: PMC5056504 DOI: 10.1038/srep34916] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 09/21/2016] [Indexed: 12/16/2022] Open
Abstract
Huntington’s disease (HD) results from expansions of polyglutamine stretches (polyQ) in the huntingtin protein (Htt) that promote protein aggregation, neurodegeneration, and death. Since the diversity and sizes of the soluble Htt-polyQ aggregates that have been linked to cytotoxicity are unknown, we investigated soluble Htt-polyQ aggregates using analytical ultracentrifugation. Soon after induction in a yeast HD model system, non-toxic Htt-25Q and cytotoxic Htt-103Q both formed soluble aggregates 29S to 200S in size. Because current models indicate that Htt-25Q does not form soluble aggregates, reevaluation of previous studies may be necessary. Only Htt-103Q aggregation behavior changed, however, with time. At 6 hr mid-sized aggregates (33S to 84S) and large aggregates (greater than 100S) became present while at 24 hr primarily only mid-sized aggregates (20S to 80S) existed. Multiple factors that decreased cytotoxicity of Htt-103Q (changing the length of or sequences adjacent to the polyQ, altering ploidy or chaperone dosage, or deleting anti-aging factors) altered the Htt-103Q aggregation pattern in which the suite of mid-sized aggregates at 6 hr were most correlative with cytotoxicity. Hence, the amelioration of HD and other neurodegenerative diseases may require increased attention to and discrimination of the dynamic alterations in soluble aggregation processes.
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Abstract
Overexpression experiments are sometimes considered as qualitative experiments designed to identify novel proteins and study their function. However, in order to draw conclusions regarding protein overexpression through association analyses using large-scale biological data sets, we need to recognize the quantitative nature of overexpression experiments. Here I discuss the quantitative features of two different types of overexpression experiment: absolute and relative. I also introduce the four primary mechanisms involved in growth defects caused by protein overexpression: resource overload, stoichiometric imbalance, promiscuous interactions, and pathway modulation associated with the degree of overexpression.
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Affiliation(s)
- Hisao Moriya
- Research Core for Interdisciplinary Sciences, Okayama University, Okayama 700-8530, Japan
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12
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Papsdorf K, Kaiser CJO, Drazic A, Grötzinger SW, Haeßner C, Eisenreich W, Richter K. Polyglutamine toxicity in yeast induces metabolic alterations and mitochondrial defects. BMC Genomics 2015; 16:662. [PMID: 26335097 PMCID: PMC4558792 DOI: 10.1186/s12864-015-1831-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 08/07/2015] [Indexed: 11/14/2022] Open
Abstract
Background Protein aggregation and its pathological effects are the major cause of several neurodegenerative diseases. In Huntington’s disease an elongated stretch of polyglutamines within the protein Huntingtin leads to increased aggregation propensity. This induces cellular defects, culminating in neuronal loss, but the connection between aggregation and toxicity remains to be established. Results To uncover cellular pathways relevant for intoxication we used genome-wide analyses in a yeast model system and identify fourteen genes that, if deleted, result in higher polyglutamine toxicity. Several of these genes, like UGO1, ATP15 and NFU1 encode mitochondrial proteins, implying that a challenged mitochondrial system may become dysfunctional during polyglutamine intoxication. We further employed microarrays to decipher the transcriptional response upon polyglutamine intoxication, which exposes an upregulation of genes involved in sulfur and iron metabolism and mitochondrial Fe-S cluster formation. Indeed, we find that in vivo iron concentrations are misbalanced and observe a reduction in the activity of the prominent Fe-S cluster containing protein aconitase. Like in other yeast strains with impaired mitochondria, non-fermentative growth is impossible after intoxication with the polyglutamine protein. NMR-based metabolic analyses reveal that mitochondrial metabolism is reduced, leading to accumulation of metabolic intermediates in polyglutamine-intoxicated cells. Conclusion These data show that damages to the mitochondrial system occur in polyglutamine intoxicated yeast cells and suggest an intricate connection between polyglutamine-induced toxicity, mitochondrial functionality and iron homeostasis in this model system. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1831-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Katharina Papsdorf
- Department Chemie, Lehrstuhl für Biotechnologie, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany.
| | - Christoph J O Kaiser
- Department Chemie, Fachgebiet Elektronenmikroskopie, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany.
| | - Adrian Drazic
- Department Chemie, Lehrstuhl für Biotechnologie, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany.
| | - Stefan W Grötzinger
- Biological and Organometallic Laboratories, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia.
| | - Carmen Haeßner
- Department Chemie, Fachgebiet Anorganische Chemie, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany.
| | - Wolfgang Eisenreich
- Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany.
| | - Klaus Richter
- Department Chemie, Lehrstuhl für Biotechnologie, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany.
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Protein folding, misfolding and quality control: the role of molecular chaperones. Essays Biochem 2014; 56:53-68. [DOI: 10.1042/bse0560053] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Cells have to cope with stressful conditions and adapt to changing environments. Heat stress, heavy metal ions or UV stress induce damage to cellular proteins and disturb the balanced status of the proteome. The adjusted balance between folded and folding proteins, called protein homoeostasis, is required for every aspect of cellular functionality. Protective proteins called chaperones are expressed under extreme conditions in order to prevent aggregation of cellular proteins and safeguard protein quality. These chaperones co-operate during de novo folding, refolding and disaggregation of damaged proteins and in many cases refold them to their functional state. Even under physiological conditions these machines support protein homoeostasis and maintain the balance between de novo folding and degradation. Mutations generating unstable proteins, which are observed in numerous human diseases such as Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis and cystic fibrosis, also challenge the protein quality control system. A better knowledge of how the protein homoeostasis system is regulated will lead to an improved understanding of these diseases and provide potential targets for therapy.
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Abstract
Prions (infectious proteins) cause fatal neurodegenerative diseases in mammals. In the yeast Saccharomyces cerevisiae, many toxic and lethal variants of the [PSI+] and [URE3] prions have been identified in laboratory strains, although some commonly studied variants do not seem to impair cell growth. Phylogenetic analysis has revealed four major clades of S. cerevisiae that share histories of two prion proteins and largely correspond to different ecological niches of yeast. The [PIN+] prion was most prevalent in commercialized niches, infrequent among wine/vineyard strains, and not observed in ancestral isolates. As previously reported, the [PSI+] and [URE3] prions are not found in any of these strains. Patterns of heterozygosity revealed genetic mosaicism and indicated extensive outcrossing among divergent strains in commercialized environments. In contrast, ancestral isolates were all homozygous and wine/vineyard strains were closely related to each other and largely homozygous. Cellular growth patterns were highly variable within and among clades, although ancestral isolates were the most efficient sporulators and domesticated strains showed greater tendencies for flocculation. [PIN+]-infected strains had a significantly higher likelihood of polyploidy, showed a higher propensity for flocculation compared to uninfected strains, and had higher sporulation efficiencies compared to domesticated, uninfected strains. Extensive phenotypic variability among strains from different environments suggests that S. cerevisiae is a niche generalist and that most wild strains are able to switch from asexual to sexual and from unicellular to multicellular growth in response to environmental conditions. Our data suggest that outbreeding and multicellular growth patterns adapted for domesticated environments are ecological risk factors for the [PIN+] prion in wild yeast.
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Gaytán BD, Vulpe CD. Functional toxicology: tools to advance the future of toxicity testing. Front Genet 2014; 5:110. [PMID: 24847352 PMCID: PMC4017141 DOI: 10.3389/fgene.2014.00110] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 04/12/2014] [Indexed: 11/16/2022] Open
Abstract
The increased presence of chemical contaminants in the environment is an undeniable concern to human health and ecosystems. Historically, by relying heavily upon costly and laborious animal-based toxicity assays, the field of toxicology has often neglected examinations of the cellular and molecular mechanisms of toxicity for the majority of compounds—information that, if available, would strengthen risk assessment analyses. Functional toxicology, where cells or organisms with gene deletions or depleted proteins are used to assess genetic requirements for chemical tolerance, can advance the field of toxicity testing by contributing data regarding chemical mechanisms of toxicity. Functional toxicology can be accomplished using available genetic tools in yeasts, other fungi and bacteria, and eukaryotes of increased complexity, including zebrafish, fruit flies, rodents, and human cell lines. Underscored is the value of using less complex systems such as yeasts to direct further studies in more complex systems such as human cell lines. Functional techniques can yield (1) novel insights into chemical toxicity; (2) pathways and mechanisms deserving of further study; and (3) candidate human toxicant susceptibility or resistance genes.
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Affiliation(s)
- Brandon D Gaytán
- Department of Nutritional Science and Toxicology, University of California Berkeley Berkeley, CA, USA
| | - Chris D Vulpe
- Department of Nutritional Science and Toxicology, University of California Berkeley Berkeley, CA, USA
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16
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Holmes WM, Klaips CL, Serio TR. Defining the limits: Protein aggregation and toxicity in vivo. Crit Rev Biochem Mol Biol 2014; 49:294-303. [PMID: 24766537 DOI: 10.3109/10409238.2014.914151] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Abstract others complementary, to resolve mis-folded proteins when they arise, ranging from refolding through the action of molecular chaperones to elimination through regulated proteolytic mechanisms. These protein quality control pathways are sufficient, under normal conditions, to maintain a functioning proteome, but in response to diverse environmental, genetic and/or stochastic events, protein mis-folding exceeds the corrective capacity of these pathways, leading to the accumulation of aggregates and ultimately toxicity. Particularly devastating examples of these effects include certain neurodegenerative diseases, such as Huntington's Disease, which are associated with the expansion of polyglutamine tracks in proteins. In these cases, protein mis-folding and aggregation are clear contributors to pathogenesis, but uncovering the precise mechanistic links between the two events remains an area of active research. Studies in the yeast Saccharomyces cerevisiae and other model systems have uncovered previously unanticipated complexity in aggregation pathways, the contributions of protein quality control processes to them and the cellular perturbations that result from them. Together these studies suggest that aggregate interactions and localization, rather than their size, are the crucial considerations in understanding the molecular basis of toxicity.
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Affiliation(s)
- William M Holmes
- Biology Department, College of the Holy Cross , Worcester, MA , USA and
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