1
|
Kumar M, Tyagi N, Faruq M. The molecular mechanisms of spinocerebellar ataxias for DNA repeat expansion in disease. Emerg Top Life Sci 2023; 7:289-312. [PMID: 37668011 DOI: 10.1042/etls20230013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 08/01/2023] [Accepted: 08/16/2023] [Indexed: 09/06/2023]
Abstract
Spinocerebellar ataxias (SCAs) are a heterogenous group of neurodegenerative disorders which commonly inherited in an autosomal dominant manner. They cause muscle incoordination due to degeneration of the cerebellum and other parts of nervous system. Out of all the characterized (>50) SCAs, 14 SCAs are caused due to microsatellite repeat expansion mutations. Repeat expansions can result in toxic protein gain-of-function, protein loss-of-function, and/or RNA gain-of-function effects. The location and the nature of mutation modulate the underlying disease pathophysiology resulting in varying disease manifestations. Potential toxic effects of these mutations likely affect key major cellular processes such as transcriptional regulation, mitochondrial functioning, ion channel dysfunction and synaptic transmission. Involvement of several common pathways suggests interlinked function of genes implicated in the disease pathogenesis. A better understanding of the shared and distinct molecular pathogenic mechanisms in these diseases is required to develop targeted therapeutic tools and interventions for disease management. The prime focus of this review is to elaborate on how expanded 'CAG' repeats contribute to the common modes of neurotoxicity and their possible therapeutic targets in management of such devastating disorders.
Collapse
Affiliation(s)
- Manish Kumar
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India
| | - Nishu Tyagi
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India
| | - Mohammed Faruq
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India
| |
Collapse
|
2
|
Gropp MHM, Klaips CL, Hartl FU. Formation of toxic oligomers of polyQ-expanded Huntingtin by prion-mediated cross-seeding. Mol Cell 2022; 82:4290-4306.e11. [PMID: 36272412 DOI: 10.1016/j.molcel.2022.09.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 08/22/2022] [Accepted: 09/28/2022] [Indexed: 11/05/2022]
Abstract
Manifestation of aggregate pathology in Huntington's disease is thought to be facilitated by a preferential vulnerability of affected brain cells to age-dependent proteostatic decline. To understand how specific cellular backgrounds may facilitate pathologic aggregation, we utilized the yeast model in which polyQ-expanded Huntingtin forms aggregates only when the endogenous prion-forming protein Rnq1 is in its amyloid-like prion [PIN+] conformation. We employed optogenetic clustering of polyQ protein as an orthogonal method to induce polyQ aggregation in prion-free [pin-] cells. Optogenetic aggregation circumvented the prion requirement for the formation of detergent-resistant polyQ inclusions but bypassed the formation of toxic polyQ oligomers, which accumulated specifically in [PIN+] cells. Reconstitution of aggregation in vitro suggested that these polyQ oligomers formed through direct templating on Rnq1 prions. These findings shed light on the mechanism of prion-mediated formation of oligomers, which may play a role in triggering polyQ pathology in the patient brain.
Collapse
Affiliation(s)
- Michael H M Gropp
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Courtney L Klaips
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany; Department of Biomedical Sciences of Cells & Systems, University Medical Center Groningen, Antonius Deusinglaan 1, 9713AV Groningen, the Netherlands.
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.
| |
Collapse
|
3
|
Ngo V, Brickenden A, Liu H, Yeung C, Choy WY, Duennwald ML. A novel yeast model detects Nrf2 and Keap1 interactions with Hsp90. Dis Model Mech 2022; 15:274138. [PMID: 35088844 PMCID: PMC9016900 DOI: 10.1242/dmm.049258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 01/11/2022] [Indexed: 11/20/2022] Open
Abstract
Nrf2 is the master transcriptional regulator of cellular responses against oxidative stress. It is chiefly regulated by Keap1, a substrate adaptor protein that mediates Nrf2 degradation. Nrf2 activity is also influenced by many other protein interactions that provide Keap1-independent regulation. To study Nrf2 regulation, we established and characterized yeast models expressing human Nrf2 (also known as NFE2L2), Keap1 and other proteins that interact with and regulate Nrf2. Yeast models have been well established as powerful tools to study protein function and genetic and physical protein-protein interactions. In this work, we recapitulate previously described Nrf2 interactions in yeast and discover that Nrf2 interacts with the molecular chaperone Hsp90. Our work establishes yeast as a useful tool to study Nrf2 interactions and provides new insight into the crosstalk between the antioxidant response and the heat shock response. Summary: We studied the interactions of human Nrf2 in a novel budding yeast model. We recapitulate previously described Nrf2 interactions and discover that Nrf2 interacts with Hsp90, establishing yeast as a useful tool to study Nrf2 interactions.
Collapse
Affiliation(s)
- Vy Ngo
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Anne Brickenden
- Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Hansen Liu
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Cynthia Yeung
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Wing-Yiu Choy
- Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Martin L Duennwald
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| |
Collapse
|
4
|
Kielar C, Morton AJ. Early Neurodegeneration in R6/2 Mice Carrying the Huntington's Disease Mutation with a Super-Expanded CAG Repeat, Despite Normal Lifespan. J Huntingtons Dis 2019; 7:61-76. [PMID: 29480204 DOI: 10.3233/jhd-170265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The threshold of CAG repeat expansion in the HTT gene that causes HD is 36 CAG repeats, although 'superlong' expansions are found in individual neurons in postmortem brains. Previously, we showed that, compared to mice with <250 CAG repeats, onset of disease in R6/2 mice carrying superlong (>440) CAG repeat expansions was delayed, and disease progression was slower. Inclusion pathology also differed from 250 CAG repeat mice, being dominated by a novel kind of extranuclear neuronal inclusion (nENNI) that resembles a class of aggregate seen in patients with the adult onset form of HD. Here, we characterised neuropathology in R6/2 mice with >400 CAG repeats using light and electron microscopy. nENNIs were found with increased frequency and wider distribution with age. Some nENNIs appear to 'mature' as the disease develops, developing a multi-layered cored structure. Mice with superlong CAG repeats do not develop clinical signs until they are around 30-40 weeks of age, and they attain a normal life span (>2 years). Nevertheless, they show brain atrophy and unequivocal neuron loss from the striatum and cortex by 22 weeks of age, an age at which similar pathology is seen in 250 CAG repeat mice. Since this time-point is 'end stage' for a 250 CAG mouse, but very far (at least 18 months) from end stage for a > 440 CAG repeat mouse, our data confirm that the appearance of clinical signs, the formation of inclusions, and neurodegeneration are processes that progress independently. A better understanding of the relationship between CAG repeat length, neurodegenerative pathways, and clinical behavioural signs is essential, if we are to find strategies to delay or reverse the course of this disease.
Collapse
Affiliation(s)
- Catherine Kielar
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - A Jennifer Morton
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| |
Collapse
|
5
|
Abstract
The spinocerebellar ataxias (SCAs) are a genetically heterogeneous group of autosomal dominantly inherited progressive disorders, the clinical hallmark of which is loss of balance and coordination accompanied by slurred speech; onset is most often in adult life. Genetically, SCAs are grouped as repeat expansion SCAs, such as SCA3/Machado-Joseph disease (MJD), and rare SCAs that are caused by non-repeat mutations, such as SCA5. Most SCA mutations cause prominent damage to cerebellar Purkinje neurons with consecutive cerebellar atrophy, although Purkinje neurons are only mildly affected in some SCAs. Furthermore, other parts of the nervous system, such as the spinal cord, basal ganglia and pontine nuclei in the brainstem, can be involved. As there is currently no treatment to slow or halt SCAs (many SCAs lead to premature death), the clinical care of patients with SCA focuses on managing the symptoms through physiotherapy, occupational therapy and speech therapy. Intense research has greatly expanded our understanding of the pathobiology of many SCAs, revealing that they occur via interrelated mechanisms (including proteotoxicity, RNA toxicity and ion channel dysfunction), and has led to the identification of new targets for treatment development. However, the development of effective therapies is hampered by the heterogeneity of the SCAs; specific therapeutic approaches may be required for each disease.
Collapse
|
6
|
Chen JY, Parekh M, Seliman H, Bakshinskaya D, Dai W, Kwan K, Chen KY, Liu AYC. Heat shock promotes inclusion body formation of mutant huntingtin (mHtt) and alleviates mHtt-induced transcription factor dysfunction. J Biol Chem 2018; 293:15581-15593. [PMID: 30143534 PMCID: PMC6177601 DOI: 10.1074/jbc.ra118.002933] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 08/22/2018] [Indexed: 01/08/2023] Open
Abstract
PolyQ-expanded huntingtin (mHtt) variants form aggregates, termed inclusion bodies (IBs), in individuals with and models of Huntington's disease (HD). The role of IB versus diffusible mHtt in neurotoxicity remains unclear. Using a ponasterone (PA)-inducible cell model of HD, here we evaluated the effects of heat shock on the appearance and functional outcome of Htt103QExon1-EGFP expression. Quantitative image analysis indicated that 80-90% of this mHtt protein initially appears as "diffuse" signals in the cytosol, with IBs forming at high mHtt expression. A 2-h heat shock during the PA induction reduced the diffuse signal, but greatly increased mHtt IB formation in both cytosol and nucleus. Dose- and time-dependent mHtt expression suggested that nucleated polymerization drives IB formation. RNA-mediated knockdown of heat shock protein 70 (HSP70) and heat shock cognate 70 protein (HSC70) provided evidence for their involvement in promoting diffuse mHtt to form IBs. Reporter gene assays assessing the impacts of diffuse versus IB mHtt showed concordance of diffuse mHtt expression with the repression of heat shock factor 1, cAMP-responsive element-binding protein (CREB), and NF-κB activity. CREB repression was reversed by heat shock coinciding with mHtt IB formation. In an embryonic striatal neuron-derived HD model, the chemical chaperone sorbitol similarly promoted the structuring of diffuse mHtt into IBs and supported cell survival under stress. Our results provide evidence that mHtt IB formation is a chaperone-supported cellular coping mechanism that depletes diffusible mHtt conformers, alleviates transcription factor dysfunction, and promotes neuron survival.
Collapse
Affiliation(s)
- Justin Y Chen
- From the Department of Cell Biology and Neuroscience and
| | - Miloni Parekh
- From the Department of Cell Biology and Neuroscience and
| | - Hadear Seliman
- From the Department of Cell Biology and Neuroscience and
| | | | - Wei Dai
- From the Department of Cell Biology and Neuroscience and
| | - Kelvin Kwan
- From the Department of Cell Biology and Neuroscience and
| | - Kuang Yu Chen
- Department of Chemistry and Chemical Biology, Rutgers State University of New Jersey, Piscataway, New Jersey 08854
| | - Alice Y C Liu
- From the Department of Cell Biology and Neuroscience and
| |
Collapse
|
7
|
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.
Collapse
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
| | | |
Collapse
|
8
|
Zhao Y, Zurawel AA, Jenkins NP, Duennwald ML, Cheng C, Kettenbach AN, Supattapone S. Comparative Analysis of Mutant Huntingtin Binding Partners in Yeast Species. Sci Rep 2018; 8:9554. [PMID: 29934597 PMCID: PMC6015068 DOI: 10.1038/s41598-018-27900-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 06/12/2018] [Indexed: 12/21/2022] Open
Abstract
Huntington's disease is caused by the pathological expansion of a polyglutamine (polyQ) stretch in Huntingtin (Htt), but the molecular mechanisms by which polyQ expansion in Htt causes toxicity in selective neuronal populations remain poorly understood. Interestingly, heterologous expression of expanded polyQ Htt is toxic in Saccharomyces cerevisiae cells, but has no effect in Schizosaccharomyces pombe, a related yeast species possessing very few endogenous polyQ or Q/N-rich proteins. Here, we used a comprehensive and unbiased mass spectrometric approach to identify proteins that bind Htt in a length-dependent manner in both species. Analysis of the expanded polyQ-associated proteins reveals marked enrichment of proteins that are localized to and play functional roles in nucleoli and mitochondria in S. cerevisiae, but not in S. pombe. Moreover, expanded polyQ Htt appears to interact preferentially with endogenous polyQ and Q/N-rich proteins, which are rare in S. pombe, as well as proteins containing coiled-coil motifs in S. cerevisiae. Taken together, these results suggest that polyQ expansion of Htt may cause cellular toxicity in S. cerevisiae by sequestering endogenous polyQ and Q/N-rich proteins, particularly within nucleoli and mitochondria.
Collapse
Affiliation(s)
- Yanding Zhao
- Departments of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States
| | - Ashley A Zurawel
- Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States
| | - Nicole P Jenkins
- Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States
| | - Martin L Duennwald
- Department of Pathology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Chao Cheng
- Departments of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States
- Biomedical Data Sciences, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States
| | - Arminja N Kettenbach
- Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States
| | - Surachai Supattapone
- Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States.
- Medicine, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire, 03755, United States.
| |
Collapse
|
9
|
Higgins R, Kabbaj MH, Hatcher A, Wang Y. The absence of specific yeast heat-shock proteins leads to abnormal aggregation and compromised autophagic clearance of mutant Huntingtin proteins. PLoS One 2018; 13:e0191490. [PMID: 29346421 PMCID: PMC5773196 DOI: 10.1371/journal.pone.0191490] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 01/05/2018] [Indexed: 11/25/2022] Open
Abstract
The functionality of a protein depends on its correct folding, but newly synthesized proteins are susceptible to aberrant folding and aggregation. Heat shock proteins (HSPs) function as molecular chaperones that aid in protein folding and the degradation of misfolded proteins. Trinucleotide (CAG) repeat expansion in the Huntingtin gene (HTT) results in the expression of misfolded Huntingtin protein (Htt), which contributes to the development of Huntington’s disease. We previously found that the degradation of mutated Htt with polyQ expansion (Htt103QP) depends on both ubiquitin proteasome system and autophagy. However, the role of heat shock proteins in the clearance of mutated Htt remains poorly understood. Here, we report that cytosolic Hsp70 (Ssa family), its nucleotide exchange factors (Sse1 and Fes1), and a Hsp40 co-chaperone (Ydj1) are required for inclusion body formation of Htt103QP proteins and their clearance via autophagy. Extended induction of Htt103QP-GFP leads to the formation of a single inclusion body in wild-type yeast cells, but mutant cells lacking these HSPs exhibit increased number of Htt103QP aggregates. Most notably, we detected more aggregated forms of Htt103QP in sse1Δ mutant cells using an agarose gel assay. Increased protein aggregates are also observed in these HSP mutants even in the absence Htt103QP overexpression. Importantly, these HSPs are required for autophagy-mediated Htt103QP clearance, but are less critical for proteasome-dependent degradation. These findings suggest a chaperone network that facilitates inclusion body formation of misfolded proteins and the subsequent autophagic clearance.
Collapse
Affiliation(s)
- Ryan Higgins
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States of America
| | - Marie-Helene Kabbaj
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States of America
| | - Alexa Hatcher
- College of Nursing, Florida State University, Tallahassee, Florida, United States of America
| | - Yanchang Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States of America
- * E-mail:
| |
Collapse
|
10
|
Abstract
Disruption of protein quality control can be detrimental, having toxic effects on single cell organisms and contributing to neurodegenerative diseases such as Alzheimer's, Parkinson's and Huntington's in humans. Here, we examined the effects of polyglutamine (polyQ) aggregation in a major fungal pathogen of humans, Candida albicans, with the goal of identifying new approaches to disable this fungus. However, we discovered that expression of polyQ stretches up to 230Q had no effect on C. albicans ability to grow and withstand proteotoxic stress. Bioinformatics analysis demonstrates that C. albicans has a similarly glutamine-rich proteome to the unicellular fungus Saccharomyces cerevisiae, which exhibits polyQ toxicity with as few as 72Q. Surprisingly, global transcriptional profiles indicated no significant change upon induction of up to 230Q. Proteomic analysis highlighted two key interactors of 230Q, Sis1 and Sgt2; however, loss of either protein had no additional effect on C. albicans toxicity. Our data suggest that C. albicans has evolved powerful mechanisms to overcome the toxicity associated with aggregation-prone proteins, providing a unique model for studying polyQ-associated diseases.
Collapse
|
11
|
Bonanomi M, Visentin C, Invernizzi G, Tortora P, Regonesi ME. The Toxic Effects of Pathogenic Ataxin-3 Variants in a Yeast Cellular Model. PLoS One 2015; 10:e0129727. [PMID: 26052945 PMCID: PMC4460139 DOI: 10.1371/journal.pone.0129727] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 05/12/2015] [Indexed: 12/22/2022] Open
Abstract
Ataxin-3 (AT3) is a deubiquitinating enzyme that triggers an inherited neurodegenerative disorder, spinocerebellar ataxia type 3, when its polyglutamine (polyQ) stretch close to the C-terminus exceeds a critical length. AT3 variants carrying the expanded polyQ are prone to associate with each other into amyloid toxic aggregates, which are responsible for neuronal death with ensuing neurodegeneration. We employed Saccharomyces cerevisiae as a eukaryotic cellular model to better clarify the mechanism by which AT3 triggers the disease. We expressed three variants: one normal (Q26), one expanded (Q85) and one truncated for a region lying from the beginning of its polyQ stretch to the end of the protein (291Δ). We found that the expression of the expanded form caused reduction in viability, accumulation of reactive oxygen species, imbalance of the antioxidant defense system and loss in cell membrane integrity, leading to necrotic death. The truncated variant also exerted a qualitatively similar, albeit milder, effect on cell growth and cytotoxicity, which points to the involvement of also non-polyQ regions in cytotoxicity. Guanidine hydrochloride, a well-known inhibitor of the chaperone Hsp104, almost completely restored wild-type survival rate of both 291Δ- and Q85-expressing strains. This suggests that AT3 aggregation and toxicity is mediated by prion forms of yeast proteins, as this chaperone plays a key role in their propagation.
Collapse
Affiliation(s)
- Marcella Bonanomi
- Department of Biotechnologies and Biosciences, University of Milano-Bicocca, Milan, Italy
| | - Cristina Visentin
- Department of Biotechnologies and Biosciences, University of Milano-Bicocca, Milan, Italy
| | - Gaetano Invernizzi
- Department of Biotechnologies and Biosciences, University of Milano-Bicocca, Milan, Italy
| | - Paolo Tortora
- Department of Biotechnologies and Biosciences, University of Milano-Bicocca, Milan, Italy
- Milan Center of Neuroscience (NeuroMI), Milan, Italy
- * E-mail:
| | - Maria Elena Regonesi
- Milan Center of Neuroscience (NeuroMI), Milan, Italy
- Department of Statistics and Quantitative Methods, University of Milano-Bicocca, Milan, Italy
| |
Collapse
|
12
|
Braun RJ. Ubiquitin-dependent proteolysis in yeast cells expressing neurotoxic proteins. Front Mol Neurosci 2015; 8:8. [PMID: 25814926 PMCID: PMC4357299 DOI: 10.3389/fnmol.2015.00008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 02/24/2015] [Indexed: 01/16/2023] Open
Abstract
Critically impaired protein degradation is discussed to contribute to neurodegenerative disorders, including Parkinson's, Huntington's, Alzheimer's, and motor neuron diseases. Misfolded, aggregated, or surplus proteins are efficiently degraded via distinct protein degradation pathways, including the ubiquitin-proteasome system, autophagy, and vesicular trafficking. These pathways are regulated by covalent modification of target proteins with the small protein ubiquitin and are evolutionary highly conserved from humans to yeast. The yeast Saccharomyces cerevisiae is an established model for deciphering mechanisms of protein degradation, and for the elucidation of pathways underlying programmed cell death. The expression of human neurotoxic proteins triggers cell death in yeast, with neurotoxic protein-specific differences. Therefore, yeast cell death models are suitable for analyzing the role of protein degradation pathways in modulating cell death upon expression of disease-causing proteins. This review summarizes which protein degradation pathways are affected in these yeast models, and how they are involved in the execution of cell death. I will discuss to which extent this mimics the situation in other neurotoxic models, and how this may contribute to a better understanding of human disorders.
Collapse
Affiliation(s)
- Ralf J Braun
- Institut für Zellbiologie, Universität Bayreuth Bayreuth, Germany
| |
Collapse
|
13
|
Deciphering the roles of trehalose and Hsp104 in the inhibition of aggregation of mutant huntingtin in a yeast model of Huntington's disease. Neuromolecular Med 2013; 16:280-91. [PMID: 24248470 DOI: 10.1007/s12017-013-8275-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 11/06/2013] [Indexed: 10/26/2022]
Abstract
Despite the significant amount of experimental data available on trehalose, the molecular mechanism responsible for its intracellular stabilising properties has not emerged yet. The repair of cellular homeostasis in many protein-misfolding diseases by trehalose is credited to the disaccharide being an inducer of autophagy, a mechanism by which aggregates of misfolded proteins are cleared by the cell. In this work, we expressed the pathogenic N-terminal fragment of huntingtin in Δnth1 mutant (unable to degrade trehalose) of Saccharomyces cerevisiae BY4742 strain. We show that the presence of trehalose resulted in the partitioning of the mutant huntingtin in the soluble fraction of the cell. This led to reduced oxidative stress and improved cell survival. The beneficial effect was independent of the expression of the major cellular antioxidant enzyme, superoxide dismutase. Additionally, trehalose led to the overexpression of the heat shock protein, Hsp104p, in mutant huntingtin-expressing cells, and resulted in rescue of the endocytotic defect in the yeast cell. We propose that at least in the initial stages of aggregation, trehalose functions as a stabiliser, increasing the level of monomeric mutant huntingtin protein, with its concomitant beneficial effects, in addition to its role as an inducer of autophagy.
Collapse
|
14
|
Elmallah MIY, Borgmeyer U, Betzel C, Redecke L. Impact of methionine oxidation as an initial event on the pathway of human prion protein conversion. Prion 2013; 7:404-11. [PMID: 24121542 DOI: 10.4161/pri.26745] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Prion diseases comprise a group of fatal neurodegenerative disorders characterized by the autocatalytic conversion of the cellular prion protein PrP(C) into the infectious misfolded isoform PrP(Sc). Increasing evidence supports a specific role of oxidative stress in the onset of pathogenesis. Although the associated molecular mechanisms remain to be elucidated in detail, several studies currently suggest that methionine oxidation already detected in misfolded PrP(Sc) destabilizes the native PrP fold as an early event in the conversion pathway. To obtain more insights about the specific impact of surface-exposed methionine residues on the oxidative-induced conversion of human PrP we designed, produced, and comparatively investigated two new pseudosulfoxidation mutants of human PrP 121-231 that comprises the well-folded C-terminal domain. Applying circular dichroism spectroscopy and dynamic light scattering techniques we showed that pseudosulfoxidation of all surface exposed Met residues formed a monomeric molten globule-like species with striking similarities to misfolding intermediates recently reported by other groups. However, individual pseudosulfoxidation at the polymorphic M129 site did not significantly contribute to the structural destabilization. Further metal-induced oxidation of the partly unfolded pseudosulfoxidation mutant resulted in the formation of an oligomeric state that shares a comparable size and stability with PrP oligomers detected after the application of different other triggers for structural conversion, indicating a generic misfolding pathway of PrP. The obtained results highlight the specific importance of methionine oxidation at surface exposed residues for PrP misfolding, strongly supporting the hypothesis that increased oxidative stress could be one causative event for sporadic prion diseases and other neurodegenerative disorders.
Collapse
Affiliation(s)
- Mohammed I Y Elmallah
- Institute of Biochemistry and Molecular Biology; Department of Chemistry; University of Hamburg, c/o DESY; Hamburg, Germany
| | - Uwe Borgmeyer
- Institute for Molecular and Cellular Cognition; Center for Molecular Neurobiology (ZMNH); University Medical Center Eppendorf; Hamburg, Germany
| | - Christian Betzel
- Institute of Biochemistry and Molecular Biology; Department of Chemistry; University of Hamburg, c/o DESY; Hamburg, Germany
| | - Lars Redecke
- Joint Laboratory for Structural Biology of Infection and Inflammation; Institute of Biochemistry and Molecular Biology; University of Hamburg; and Institute of Biochemistry; University of Lübeck, c/o DESY; Hamburg, Germany
| |
Collapse
|
15
|
Chafekar SM, Wisén S, Thompson AD, Echeverria A, Walter GM, Evans CG, Makley LN, Gestwicki JE, Duennwald ML. Pharmacological tuning of heat shock protein 70 modulates polyglutamine toxicity and aggregation. ACS Chem Biol 2012; 7:1556-64. [PMID: 22709427 PMCID: PMC3448832 DOI: 10.1021/cb300166p] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Nine neurodegenerative disorders are caused by the abnormal expansion of polyglutamine (polyQ) regions within distinct proteins. Genetic and biochemical evidence has documented that the molecular chaperone, heat shock protein 70 (Hsp70), modulates polyQ toxicity and aggregation, yet it remains unclear how Hsp70 might be used as a potential therapeutic target in polyQ-related diseases. We have utilized a pair of membrane-permeable compounds that tune the activity of Hsp70 by either stimulating or by inhibiting its ATPase functions. Using these two pharmacological agents in both yeast and PC12 cell models of polyQ aggregation and toxicity, we were surprised to find that stimulating Hsp70 solubilized polyQ conformers and simultaneously exacerbated polyQ-mediated toxicity. By contrast, inhibiting Hsp70 ATPase activity protected against polyQ toxicity and promoted aggregation. These findings clarify the role of Hsp70 as a possible drug target in polyQ disorders and suggest that Hsp70 uses ATP hydrolysis to help partition polyQ proteins into structures with varying levels of proteotoxicity. Our results thus support an emerging concept in which certain kinds of polyQ aggregates may be protective, while more soluble polyQ species are toxic.
Collapse
Affiliation(s)
| | - Susanne Wisén
- University of Michigan, Departments of Pathology and the Life Sciences Institute, Ann Arbor, MI 48109-2216
| | - Andrea D. Thompson
- University of Michigan, Departments of Pathology and the Life Sciences Institute, Ann Arbor, MI 48109-2216
| | | | - Gladis M. Walter
- University of Michigan, Departments of Pathology and the Life Sciences Institute, Ann Arbor, MI 48109-2216
| | - Christopher G. Evans
- University of Michigan, Departments of Pathology and the Life Sciences Institute, Ann Arbor, MI 48109-2216
| | - Leah N. Makley
- University of Michigan, Departments of Pathology and the Life Sciences Institute, Ann Arbor, MI 48109-2216
| | - Jason E. Gestwicki
- University of Michigan, Departments of Pathology and the Life Sciences Institute, Ann Arbor, MI 48109-2216
| | | |
Collapse
|
16
|
Abstract
The concept of a prion as an infectious self-propagating protein isoform was initially proposed to explain certain mammalian diseases. It is now clear that yeast also has heritable elements transmitted via protein. Indeed, the "protein only" model of prion transmission was first proven using a yeast prion. Typically, known prions are ordered cross-β aggregates (amyloids). Recently, there has been an explosion in the number of recognized prions in yeast. Yeast continues to lead the way in understanding cellular control of prion propagation, prion structure, mechanisms of de novo prion formation, specificity of prion transmission, and the biological roles of prions. This review summarizes what has been learned from yeast prions.
Collapse
Affiliation(s)
- Susan W Liebman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557, USA.
| | | |
Collapse
|
17
|
Yeast and the AIDS virus: the odd couple. J Biomed Biotechnol 2012; 2012:549020. [PMID: 22778552 PMCID: PMC3385842 DOI: 10.1155/2012/549020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Revised: 04/14/2012] [Accepted: 04/16/2012] [Indexed: 12/13/2022] Open
Abstract
Despite being simple eukaryotic organisms, the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe have been widely used as a model to study human pathologies and the replication of human, animal, and plant viruses, as well as the function of individual viral proteins. The complete genome of S. cerevisiae was the first of eukaryotic origin to be sequenced and contains about 6,000 genes. More than 75% of the genes have an assigned function, while more than 40% share conserved sequences with known or predicted human genes. This strong homology has allowed the function of human orthologs to be unveiled starting from the data obtained in yeast. RNA plant viruses were the first to be studied in yeast. In this paper, we focus on the use of the yeast model to study the function of the proteins of human immunodeficiency virus type 1 (HIV-1) and the search for its cellular partners. This human retrovirus is the cause of AIDS. The WHO estimates that there are 33.4 million people worldwide living with HIV/AIDS, with 2.7 million new HIV infections per year and 2.0 million annual deaths due to AIDS. Current therapy is able to control the disease but there is no permanent cure or a vaccine. By using yeast, it is possible to dissect the function of some HIV-1 proteins and discover new cellular factors common to this simple cell and humans that may become potential therapeutic targets, leading to a long-lasting treatment for AIDS.
Collapse
|
18
|
Chafekar SM, Duennwald ML. Impaired heat shock response in cells expressing full-length polyglutamine-expanded huntingtin. PLoS One 2012; 7:e37929. [PMID: 22649566 PMCID: PMC3359295 DOI: 10.1371/journal.pone.0037929] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 04/30/2012] [Indexed: 01/02/2023] Open
Abstract
The molecular mechanisms by which polyglutamine (polyQ)-expanded huntingtin (Htt) causes neurodegeneration in Huntington's disease (HD) remain unclear. The malfunction of cellular proteostasis has been suggested as central in HD pathogenesis and also as a target of therapeutic interventions for the treatment of HD. We present results that offer a previously unexplored perspective regarding impaired proteostasis in HD. We find that, under non-stress conditions, the proteostatic capacity of cells expressing full length polyQ-expanded Htt is adequate. Yet, under stress conditions, the presence of polyQ-expanded Htt impairs the heat shock response, a key component of cellular proteostasis. This impaired heat shock response results in a reduced capacity to withstand the damage caused by cellular stress. We demonstrate that in cells expressing polyQ-expanded Htt the levels of heat shock transcription factor 1 (HSF1) are reduced, and, as a consequence, these cells have an impaired a heat shock response. Also, we found reduced HSF1 and HSP70 levels in the striata of HD knock-in mice when compared to wild-type mice. Our results suggests that full length, non-aggregated polyQ-expanded Htt blocks the effective induction of the heat shock response under stress conditions and may thus trigger the accumulation of cellular damage during the course of HD pathogenesis.
Collapse
Affiliation(s)
| | - Martin L. Duennwald
- Regenerative Biology Program, Boston Biomedical Research Institute, Watertown, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
19
|
Gong H, Romanova NV, Allen KD, Chandramowlishwaran P, Gokhale K, Newnam GP, Mieczkowski P, Sherman MY, Chernoff YO. Polyglutamine toxicity is controlled by prion composition and gene dosage in yeast. PLoS Genet 2012; 8:e1002634. [PMID: 22536159 PMCID: PMC3334884 DOI: 10.1371/journal.pgen.1002634] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 02/21/2012] [Indexed: 12/02/2022] Open
Abstract
Polyglutamine expansion causes diseases in humans and other mammals. One example is Huntington's disease. Fragments of human huntingtin protein having an expanded polyglutamine stretch form aggregates and cause cytotoxicity in yeast cells bearing endogenous QN-rich proteins in the aggregated (prion) form. Attachment of the proline(P)-rich region targets polyglutamines to the large perinuclear deposit (aggresome). Aggresome formation ameliorates polyglutamine cytotoxicity in cells containing only the prion form of Rnq1 protein. Here we show that expanded polyglutamines both with (poly-QP) or without (poly-Q) a P-rich stretch remain toxic in the presence of the prion form of translation termination (release) factor Sup35 (eRF3). A Sup35 derivative that lacks the QN-rich domain and is unable to be incorporated into aggregates counteracts cytotoxicity, suggesting that toxicity is due to Sup35 sequestration. Increase in the levels of another release factor, Sup45 (eRF1), due to either disomy by chromosome II containing the SUP45 gene or to introduction of the SUP45-bearing plasmid counteracts poly-Q or poly-QP toxicity in the presence of the Sup35 prion. Protein analysis confirms that polyglutamines alter aggregation patterns of Sup35 and promote aggregation of Sup45, while excess Sup45 counteracts these effects. Our data show that one and the same mode of polyglutamine aggregation could be cytoprotective or cytotoxic, depending on the composition of other aggregates in a eukaryotic cell, and demonstrate that other aggregates expand the range of proteins that are susceptible to sequestration by polyglutamines. Polyglutamine diseases, including Huntington disease, are associated with expansions of polyglutamine tracts, resulting in aggregation of respective proteins. The severity of Huntington disease is controlled by both DNA and non–DNA factors. Mechanisms of such a control are poorly understood. Polyglutamine may sequester other cellular proteins; however, different experimental models have pointed to different sequestered proteins. By using a yeast model, we demonstrate that the mechanism of polyglutamine toxicity is driven by the composition of other (endogenous) aggregates (for example, yeast prions) present in a eukaryotic cell. Although these aggregates do not necessarily cause significant toxicity on their own, they serve as mediators in protein sequestration and therefore determine which specific proteins are to be sequestered by polyglutamines. We also show that polyglutamine deposition into an aggresome, a perinuclear compartment thought to be cytoprotective, fails to ameliorate cytotoxicity in cells with certain compositions of pre-existing aggregates. Finally, we demonstrate that an increase in the dosage of a sequestered protein due to aneuploidy by a chromosome carrying a respective gene may rescue cytotoxicity. Our data shed light on genetic and epigenetic mechanisms modulating polyglutamine cytotoxicity and establish a new approach for identifying potential therapeutic targets through characterization of the endogenous aggregated proteins.
Collapse
Affiliation(s)
- He Gong
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Nina V. Romanova
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Kim D. Allen
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | | | - Kavita Gokhale
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Gary P. Newnam
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Piotr Mieczkowski
- School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Michael Y. Sherman
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Yury O. Chernoff
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- * E-mail:
| |
Collapse
|