1
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Hall D. MIL-CELL: a tool for multi-scale simulation of yeast replication and prion transmission. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2023; 52:673-704. [PMID: 37670150 PMCID: PMC10682183 DOI: 10.1007/s00249-023-01679-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/08/2023] [Accepted: 08/14/2023] [Indexed: 09/07/2023]
Abstract
The single-celled baker's yeast, Saccharomyces cerevisiae, can sustain a number of amyloid-based prions, the three most prominent examples being [URE3], [PSI+], and [PIN+]. In the laboratory, haploid S. cerevisiae cells of a single mating type can acquire an amyloid prion in one of two ways (i) spontaneous nucleation of the prion within the yeast cell, and (ii) receipt via mother-to-daughter transmission during the cell division cycle. Similarly, prions can be lost due to (i) dissolution of the prion amyloid by its breakage into non-amyloid monomeric units, or (ii) preferential donation/retention of prions between the mother and daughter during cell division. Here we present a computational tool (Monitoring Induction and Loss of prions in Cells; MIL-CELL) for modelling these four general processes using a multiscale approach describing both spatial and kinetic aspects of the yeast life cycle and the amyloid-prion behavior. We describe the workings of the model, assumptions upon which it is based and some interesting simulation results pertaining to the wave-like spread of the epigenetic prion elements through the yeast population. MIL-CELL is provided as a stand-alone GUI executable program for free download with the paper. MIL-CELL is equipped with a relational database allowing all simulated properties to be searched, collated and graphed. Its ability to incorporate variation in heritable properties means MIL-CELL is also capable of simulating loss of the isogenic nature of a cell population over time. The capability to monitor both chronological and reproductive age also makes MIL-CELL potentially useful in studies of cell aging.
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Affiliation(s)
- Damien Hall
- WPI Nano Life Science Institute, Kanazawa University, Kakumamachi, Kanazawa, Ishikawa, 920-1164, Japan.
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2
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Santiago F, Sindi S. A structured model and likelihood approach to estimate yeast prion propagon replication rates and their asymmetric transmission. PLoS Comput Biol 2022; 18:e1010107. [PMID: 35776712 PMCID: PMC9249220 DOI: 10.1371/journal.pcbi.1010107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 04/14/2022] [Indexed: 11/18/2022] Open
Abstract
Prion proteins cause a variety of fatal neurodegenerative diseases in mammals but are generally harmless to Baker’s yeast (Saccharomyces cerevisiae). This makes yeast an ideal model organism for investigating the protein dynamics associated with these diseases. The rate of disease onset is related to both the replication and transmission kinetics of propagons, the transmissible agents of prion diseases. Determining the kinetic parameters of propagon replication in yeast is complicated because the number of propagons in an individual cell depends on the intracellular replication dynamics and the asymmetric division of yeast cells within a growing yeast cell colony. We present a structured population model describing the distribution and replication of prion propagons in an actively dividing population of yeast cells. We then develop a likelihood approach for estimating the propagon replication rate and their transmission bias during cell division. We first demonstrate our ability to correctly recover known kinetic parameters from simulated data, then we apply our likelihood approach to estimate the kinetic parameters for six yeast prion variants using propagon recovery data. We find that, under our modeling framework, all variants are best described by a model with an asymmetric transmission bias. This demonstrates the strength of our framework over previous formulations assuming equal partitioning of intracellular constituents during cell division. In this work we investigate the transmissible [PSI+] phenotype in yeast. The agents responsible for this phenotype are propagons, misfolded protein aggregates of a naturally occurring protein. These propagons increase in number within a cell and are distributed between cells during division. We use mathematical modeling to infer the replication rate of propagons within cells and if propagons are transmitted equally or unequally during cell division. Prior models in this area assumed only symmetric transmission when fitting replication rates. We couple this model with a novel likelihood framework allowing us to exclude influential outliers from our datasets when inferring parameters. We find that for all six protein variants we study, propagons are transmitted asymmetrically with different biases. Our results can be reproduced with the code and data available at https://github.com/FS-CodeBase/propagon_replication_and_transmission/.
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Affiliation(s)
- Fabian Santiago
- Department of Mathematics, University of Arizona, Tucson, Arizona, United States of America
| | - Suzanne Sindi
- Department of Applied Mathematics, University of California Merced, Merced, California, United States of America
- * E-mail:
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3
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Amyloid Fragmentation and Disaggregation in Yeast and Animals. Biomolecules 2021; 11:biom11121884. [PMID: 34944528 PMCID: PMC8699242 DOI: 10.3390/biom11121884] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/10/2021] [Accepted: 12/12/2021] [Indexed: 12/29/2022] Open
Abstract
Amyloids are filamentous protein aggregates that are associated with a number of incurable diseases, termed amyloidoses. Amyloids can also manifest as infectious or heritable particles, known as prions. While just one prion is known in humans and animals, more than ten prion amyloids have been discovered in fungi. The propagation of fungal prion amyloids requires the chaperone Hsp104, though in excess it can eliminate some prions. Even though Hsp104 acts to disassemble prion fibrils, at normal levels it fragments them into multiple smaller pieces, which ensures prion propagation and accelerates prion conversion. Animals lack Hsp104, but disaggregation is performed by the same complement of chaperones that assist Hsp104 in yeast—Hsp40, Hsp70, and Hsp110. Exogenous Hsp104 can efficiently cooperate with these chaperones in animals and promotes disaggregation, especially of large amyloid aggregates, which indicates its potential as a treatment for amyloid diseases. However, despite the significant effects, Hsp104 and its potentiated variants may be insufficient to fully dissolve amyloid. In this review, we consider chaperone mechanisms acting to disassemble heritable protein aggregates in yeast and animals, and their potential use in the therapy of human amyloid diseases.
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4
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Kabani M. Extracellular Vesicles and the Propagation of Yeast Prions. Curr Top Microbiol Immunol 2021; 432:57-66. [DOI: 10.1007/978-3-030-83391-6_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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5
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Extracellular Vesicles-Encapsulated Yeast Prions and What They Can Tell Us about the Physical Nature of Propagons. Int J Mol Sci 2020; 22:ijms22010090. [PMID: 33374854 PMCID: PMC7794690 DOI: 10.3390/ijms22010090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 12/14/2020] [Accepted: 12/20/2020] [Indexed: 12/25/2022] Open
Abstract
The yeast Saccharomyces cerevisiae hosts an ensemble of protein-based heritable traits, most of which result from the conversion of structurally and functionally diverse cytoplasmic proteins into prion forms. Among these, [PSI+], [URE3] and [PIN+] are the most well-documented prions and arise from the assembly of Sup35p, Ure2p and Rnq1p, respectively, into insoluble fibrillar assemblies. Yeast prions propagate by molecular chaperone-mediated fragmentation of these aggregates, which generates small self-templating seeds, or propagons. The exact molecular nature of propagons and how they are faithfully transmitted from mother to daughter cells despite spatial protein quality control are not fully understood. In [PSI+] cells, Sup35p forms detergent-resistant assemblies detectable on agarose gels under semi-denaturant conditions and cytosolic fluorescent puncta when the protein is fused to green fluorescent protein (GFP); yet, these macroscopic manifestations of [PSI+] do not fully correlate with the infectivity measured during growth by the mean of protein infection assays. We also discovered that significant amounts of infectious Sup35p particles are exported via extracellular (EV) and periplasmic (PV) vesicles in a growth phase and glucose-dependent manner. In the present review, I discuss how these vesicles may be a source of actual propagons and a suitable vehicle for their transmission to the bud.
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6
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Mutations Outside the Ure2 Amyloid-Forming Region Disrupt [URE3] Prion Propagation and Alter Interactions with Protein Quality Control Factors. Mol Cell Biol 2020; 40:MCB.00294-20. [PMID: 32868289 DOI: 10.1128/mcb.00294-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 08/21/2020] [Indexed: 12/22/2022] Open
Abstract
The yeast prion [URE3] propagates as a misfolded amyloid form of the Ure2 protein. Propagation of amyloid-based yeast prions requires protein quality control (PQC) factors, and altering PQC abundance or activity can cure cells of prions. Yeast antiprion systems composed of PQC factors act at normal abundance to restrict establishment of the majority of prion variants that arise de novo While these systems are well described, how they or other PQC factors interact with prion proteins remains unclear. To gain insight into such interactions, we identified mutations outside the Ure2 prion-determining region that destabilize [URE3]. Despite residing in the functional domain, 16 of 17 mutants retained Ure2 activity. Four characterized mutations caused rapid loss of [URE3] yet allowed [URE3] to propagate under prion-selecting conditions. Two sensitized [URE3] to Btn2, Cur1, and Hsp42, but in different ways. Two others reduced amyloid formation in vitro Of these, one impaired prion replication and the other apparently impaired transmission. Thus, widely dispersed sites outside a prion's amyloid-forming region can contribute to prion character, and altering such sites can disrupt prion propagation by altering interactions with PQC factors.
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7
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Mechanisms for Curing Yeast Prions. Int J Mol Sci 2020; 21:ijms21186536. [PMID: 32906758 PMCID: PMC7555348 DOI: 10.3390/ijms21186536] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/31/2020] [Accepted: 09/02/2020] [Indexed: 11/24/2022] Open
Abstract
Prions are infectious proteins that self-propagate by changing from their normal folded conformation to a misfolded conformation. The misfolded conformation, which is typically rich in β-sheet, serves as a template to convert the prion protein into its misfolded conformation. In yeast, the misfolded prion proteins are assembled into amyloid fibers or seeds, which are constantly severed and transmitted to daughter cells. To cure prions in yeast, it is necessary to eliminate all the prion seeds. Multiple mechanisms of curing have been found including inhibiting severing of the prion seeds, gradual dissolution of the prion seeds, asymmetric segregation of the prion seeds between mother and daughter cells during cell division, and degradation of the prion seeds. These mechanisms, achieved by using different protein quality control machinery, are not mutually exclusive; depending on conditions, multiple mechanisms may work simultaneously to achieve curing. This review discusses the various methods that have been used to differentiate between these mechanisms of curing.
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8
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Lemarre P, Pujo-Menjouet L, Sindi SS. A unifying model for the propagation of prion proteins in yeast brings insight into the [PSI+] prion. PLoS Comput Biol 2020; 16:e1007647. [PMID: 32453794 PMCID: PMC7274466 DOI: 10.1371/journal.pcbi.1007647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 06/05/2020] [Accepted: 03/06/2020] [Indexed: 11/18/2022] Open
Abstract
The use of yeast systems to study the propagation of prions and amyloids has emerged as a crucial aspect of the global endeavor to understand those mechanisms. Yeast prion systems are intrinsically multi-scale: the molecular chemical processes are indeed coupled to the cellular processes of cell growth and division to influence phenotypical traits, observable at the scale of colonies. We introduce a novel modeling framework to tackle this difficulty using impulsive differential equations. We apply this approach to the [PSI+] yeast prion, which is associated with the misconformation and aggregation of Sup35. We build a model that reproduces and unifies previously conflicting experimental observations on [PSI+] and thus sheds light onto characteristics of the intracellular molecular processes driving aggregate replication. In particular our model uncovers a kinetic barrier for aggregate replication at low densities, meaning the change between prion or prion-free phenotype is a bi-stable transition. This result is based on the study of prion curing experiments, as well as the phenomenon of colony sectoring, a phenotype which is often ignored in experimental assays and has never been modeled. Furthermore, our results provide further insight into the effect of guanidine hydrochloride (GdnHCl) on Sup35 aggregates. To qualitatively reproduce the GdnHCl curing experiment, aggregate replication must not be completely inhibited, which suggests the existence of a mechanism different than Hsp104-mediated fragmentation. Those results are promising for further development of the [PSI+] model, but also for extending the use of this novel framework to other yeast prion or amyloid systems.
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Affiliation(s)
- Paul Lemarre
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5208, Institut Camille Jordan, 43 blvd. du 11 novembre 1918, F-69622 Villeurbanne cedex, France
- INRIA Rhônes-Alpes, INRIA, Villeurbanne, France
- Department of Applied Mathematics, University of California Merced, Merced, California, United States of America
| | - Laurent Pujo-Menjouet
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5208, Institut Camille Jordan, 43 blvd. du 11 novembre 1918, F-69622 Villeurbanne cedex, France
- INRIA Rhônes-Alpes, INRIA, Villeurbanne, France
| | - Suzanne S. Sindi
- Department of Applied Mathematics, University of California Merced, Merced, California, United States of America
- * E-mail:
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9
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Upadhyay A. Structure of proteins: Evolution with unsolved mysteries. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 149:160-172. [PMID: 31014967 DOI: 10.1016/j.pbiomolbio.2019.04.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/16/2019] [Accepted: 04/19/2019] [Indexed: 02/07/2023]
Abstract
Evolution of macromolecules could be considered as a milestone in the history of life. Nucleic acids are the long stretches of nucleotides that contain all the possible codes and information of life. On the other hand, proteins are their actual translated outcomes, or reflections of modifications in their structure that have occurred at a slow, but steady rate over a very long period of evolution. Over the years of research, biophysicists, biochemists, molecular and structural biologists have unfurled several layers of the structural convolutions in these chemical molecules; however evolutionists look over their structures through a different prism, which may or may not coincide with others. There remains a need to outline several well-known, but less discussed features of protein structures, like intrinsically disordered states, degron signals and different types of ubiquitin chains providing degradation signals, which help the cellular proteolytic machinery to identify and target the proteins towards degradation pathways. There are several important factors, which are critical for folding of proteins into their native three-dimensional conformations by the cytoplasmic chaperones; but in real time how the chaperones fold the newly synthesized polypeptide sequences into a particular three-dimensional shape within a fraction of second is still a mystery for biologists as well as mathematicians. Multiple similar unsolved or unaddressed questions need to be addressed in detail so that future line of research can dig deeper into the finer details of these structures of the proteins.
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Affiliation(s)
- Arun Upadhyay
- Department of Biochemistry, Central University of Rajasthan, Ajmer, 305817, India.
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10
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Tikhodeyev ON. The mechanisms of epigenetic inheritance: how diverse are they? Biol Rev Camb Philos Soc 2018; 93:1987-2005. [PMID: 29790249 DOI: 10.1111/brv.12429] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 04/22/2018] [Accepted: 04/27/2018] [Indexed: 12/18/2022]
Abstract
Although epigenetic inheritance (EI) is a rapidly growing field of modern biology, it still has no clear place in fundamental genetic concepts which are traditionally based on the hereditary role of DNA. Moreover, not all mechanisms of EI attract the same attention, with most studies focused on DNA methylation, histone modification, RNA interference and amyloid prionization, but relatively few considering other mechanisms such as stable inhibition of plastid translation. Herein, we discuss all known and some hypothetical mechanisms that can underlie the stable inheritance of phenotypically distinct hereditary factors that lack differences in DNA sequence. These mechanisms include (i) regulation of transcription by DNA methylation, histone modifications, and transcription factors, (ii) RNA splicing, (iii) RNA-mediated post-transcriptional silencing, (iv) organellar translation, (v) protein processing by truncation, (vi) post-translational chemical modifications, (vii) protein folding, and (viii) homologous and non-homologous protein interactions. The breadth of this list suggests that any or almost any regulatory mechanism that participates in gene expression or gene-product functioning, under certain circumstances, may produce EI. Although the modes of EI are highly variable, in many epigenetic systems, stable allelic variants can be distinguished. Irrespective of their nature, all such alleles have an underlying similarity: each is a bimodular hereditary unit, whose features depend on (i) a certain epigenetic mark (epigenetic determinant) in the DNA sequence or its product, and (ii) the DNA sequence itself (DNA determinant; if this is absent, the epigenetic allele fails to perpetuate). Thus, stable allelic epigenetic inheritance (SAEI) does not contradict the hereditary role of DNA, but involves additional molecular mechanisms with no or almost no limitations to their variety.
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Affiliation(s)
- Oleg N Tikhodeyev
- Department of Genetics & Biotechnology, Saint-Petersburg State University, Saint-Petersburg 199034, Russia
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11
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Wisniewski BT, Sharma J, Legan ER, Paulson E, Merrill SJ, Manogaran AL. Toxicity and infectivity: insights from de novo prion formation. Curr Genet 2018; 64:117-123. [PMID: 28856415 PMCID: PMC5777878 DOI: 10.1007/s00294-017-0736-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 08/15/2017] [Accepted: 08/17/2017] [Indexed: 02/07/2023]
Abstract
Prions are infectious misfolded proteins that assemble into oligomers and large aggregates, and are associated with neurodegeneration. It is believed that the oligomers contribute to cytotoxicity, although genetic and environmental factors have also been shown to have additional roles. The study of the yeast prion [PSI +] has provided valuable insights into how prions form and why they are toxic. Our recent work suggests that SDS-resistant oligomers arise and remodel early during the prion formation process, and lysates containing these newly formed oligomers are infectious. Previous work shows that toxicity is associated with prion formation and this toxicity is exacerbated by deletion of the VPS5 gene. Here, we show that newly made oligomer formation and infectivity of vps5∆ lysates are similar to wild-type strains. However using green fluorescent protein fusions, we observe that the assembly of fluorescent cytoplasmic aggregates during prion formation is different in vps5∆ strains. Instead of large immobile aggregates, vps5∆ strains have an additional population of small mobile foci. We speculate that changes in the cellular milieu in vps5∆ strains may reduce the cell's ability to efficiently recruit and sequester newly formed prion particles into central deposition sites, resulting in toxicity.
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Affiliation(s)
- Brett T Wisniewski
- Department of Biological Sciences, Marquette University, P.O. Box 1881, Milwaukee, WI, 53201-1881, USA
| | - Jaya Sharma
- Department of Biological Sciences, Marquette University, P.O. Box 1881, Milwaukee, WI, 53201-1881, USA
| | - Emily R Legan
- Department of Biological Sciences, Marquette University, P.O. Box 1881, Milwaukee, WI, 53201-1881, USA
| | - Emily Paulson
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, 53201, USA
| | - Stephen J Merrill
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, 53201, USA
| | - Anita L Manogaran
- Department of Biological Sciences, Marquette University, P.O. Box 1881, Milwaukee, WI, 53201-1881, USA.
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12
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Aslam K, Tsai CJ, Hazbun TR. The small heat shock protein Hsp31 cooperates with Hsp104 to modulate Sup35 prion aggregation. Prion 2017; 10:444-465. [PMID: 27690738 DOI: 10.1080/19336896.2016.1234574] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The yeast homolog of DJ-1, Hsp31, is a multifunctional protein that is involved in several cellular pathways including detoxification of the toxic metabolite methylglyoxal and as a protein deglycase. Prior studies ascribed Hsp31 as a molecular chaperone that can inhibit α-Syn aggregation in vitro and alleviate its toxicity in vivo. It was also shown that Hsp31 inhibits Sup35 aggregate formation in yeast, however, it is unknown if Hsp31 can modulate [PSI+] phenotype and Sup35 prionogenesis. Other small heat shock proteins, Hsp26 and Hsp42 are known to be a part of a synergistic proteostasis network that inhibits Sup35 prion formation and promotes its disaggregation. Here, we establish that Hsp31 inhibits Sup35 [PSI+] prion formation in collaboration with a well-known disaggregase, Hsp104. Hsp31 transiently prevents prion induction but does not suppress induction upon prolonged expression of Sup35 indicating that Hsp31 can be overcome by larger aggregates. In addition, elevated levels of Hsp31 do not cure [PSI+] strains indicating that Hsp31 cannot intervene in a pre-existing prion oligomerization cycle. However, Hsp31 can modulate prion status in cooperation with Hsp104 because it inhibits Sup35 aggregate formation and potentiates [PSI+] prion curing upon overexpression of Hsp104. The absence of Hsp31 reduces [PSI+] prion curing by Hsp104 without influencing its ability to rescue cellular thermotolerance. Hsp31 did not synergize with Hsp42 to modulate the [PSI+] phenotype suggesting that both proteins act on similar stages of the prion cycle. We also showed that Hsp31 physically interacts with Hsp104 and together they prevent Sup35 prion toxicity to greater extent than if they were expressed individually. These results elucidate a mechanism for Hsp31 on prion modulation that suggest it acts at a distinct step early in the Sup35 aggregation process that is different from Hsp104. This is the first demonstration of the modulation of [PSI+] status by the chaperone action of Hsp31. The delineation of Hsp31's role in the chaperone cycle has implications for understanding the role of the DJ-1 superfamily in controlling misfolded proteins in neurodegenerative disease and cancer.
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Affiliation(s)
- Kiran Aslam
- a Department of Medicinal Chemistry and Molecular Pharmacology and the Purdue University Center for Cancer Research , Purdue University , West Lafayette , IN , USA
| | - Chai-Jui Tsai
- a Department of Medicinal Chemistry and Molecular Pharmacology and the Purdue University Center for Cancer Research , Purdue University , West Lafayette , IN , USA
| | - Tony R Hazbun
- a Department of Medicinal Chemistry and Molecular Pharmacology and the Purdue University Center for Cancer Research , Purdue University , West Lafayette , IN , USA
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Marchante R, Beal DM, Koloteva-Levine N, Purton TJ, Tuite MF, Xue WF. The physical dimensions of amyloid aggregates control their infective potential as prion particles. eLife 2017; 6. [PMID: 28880146 PMCID: PMC5589414 DOI: 10.7554/elife.27109] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 08/21/2017] [Indexed: 01/29/2023] Open
Abstract
Transmissible amyloid particles called prions are associated with infectious prion diseases in mammals and inherited phenotypes in yeast. All amyloid aggregates can give rise to potentially infectious seeds that accelerate their growth. Why some amyloid seeds are highly infectious prion particles while others are less infectious or even inert, is currently not understood. To address this question, we analyzed the suprastructure and dimensions of synthetic amyloid fibrils assembled from the yeast (Saccharomyces cerevisiae) prion protein Sup35NM. We then quantified the ability of these particles to induce the [PSI+] prion phenotype in cells. Our results show a striking relationship between the length distribution of the amyloid fibrils and their ability to induce the heritable [PSI+] prion phenotype. Using a simple particle size threshold model to describe transfection activity, we explain how dimensions of amyloid fibrils are able to modulate their infectious potential as prions.
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Affiliation(s)
- Ricardo Marchante
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - David M Beal
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | | | - Tracey J Purton
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Mick F Tuite
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Wei-Feng Xue
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
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14
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Abstract
The AAA+ disaggregase Hsp104 is essential for the maintenance and inheritance of nearly all known prions of the yeast Saccharomyces cerevisiae. Uniquely for [PSI+], the prion form of the Sup35 protein, there seem to be two activities, involving differing co-chaperones, by which Hsp104 affects the inheritance of [PSI+], the prion form of the Sup35 protein. Each pathway is also involved in protection against ageing, one through disaggregation of damaged proteins and the other through their retention in the mother cell during budding. Mutations in both Hsp104 and Sup35 affect prion inheritance by one or other of these pathways, as does manipulation of either Hsp104 enzyme activity or expression, in both vegetative (budding) divisions and in sporulation. Based on our recent finding (Ness et al. in Molec Microbiol 104:125–143, 2017) we suggest that the management of the heritable prion forms of Sup35 in [PSI+] cells in sporulation may be a marker for a role for Hsp104 in rejuvenation during sporulation.
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Affiliation(s)
- Brian Cox
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK. .,Linacre College, Oxford University, St. Cross Rd, Oxford, OX1 3JA, UK.
| | - Mick Tuite
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK
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15
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Ness F, Cox BS, Wongwigkarn J, Naeimi WR, Tuite MF. Over-expression of the molecular chaperone Hsp104 inSaccharomyces cerevisiaeresults in the malpartition of [PSI+] propagons. Mol Microbiol 2017; 104:125-143. [DOI: 10.1111/mmi.13617] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2017] [Indexed: 12/11/2022]
Affiliation(s)
- Frederique Ness
- Kent Fungal Group, School of Biosciences; University of Kent; Canterbury Kent NJ CT2 7 UK
| | - Brian S. Cox
- Kent Fungal Group, School of Biosciences; University of Kent; Canterbury Kent NJ CT2 7 UK
| | - Jintana Wongwigkarn
- Kent Fungal Group, School of Biosciences; University of Kent; Canterbury Kent NJ CT2 7 UK
| | - Wesley R. Naeimi
- Kent Fungal Group, School of Biosciences; University of Kent; Canterbury Kent NJ CT2 7 UK
| | - Mick F. Tuite
- Kent Fungal Group, School of Biosciences; University of Kent; Canterbury Kent NJ CT2 7 UK
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16
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Sideri T, Yashiroda Y, Ellis DA, Rodríguez-López M, Yoshida M, Tuite MF, Bähler J. The copper transport-associated protein Ctr4 can form prion-like epigenetic determinants in Schizosaccharomyces pombe. MICROBIAL CELL 2017; 4:16-28. [PMID: 28191457 PMCID: PMC5302157 DOI: 10.15698/mic2017.01.552] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Prions are protein-based infectious entities associated with fatal brain diseases
in animals, but also modify a range of host-cell phenotypes in the budding
yeast, Saccharomyces cerevisiae. Many questions remain about
the evolution and biology of prions. Although several functionally distinct
prion-forming proteins exist in S. cerevisiae, [HET-s] of
Podospora anserina is the only other known fungal prion.
Here we investigated prion-like, protein-based epigenetic transmission in the
fission yeast Schizosaccharomyces pombe. We show that
S. pombe cells can support the formation and maintenance of
the prion form of the S. cerevisiae Sup35 translation factor
[PSI+], and that the formation and propagation
of these Sup35 aggregates is inhibited by guanidine hydrochloride, indicating
commonalities in prion propagation machineries in these evolutionary diverged
yeasts. A proteome-wide screen identified the Ctr4 copper transporter subunit as
a putative prion with a predicted prion-like domain. Overexpression of
the ctr4 gene resulted in large Ctr4 protein aggregates
that were both detergent and proteinase-K resistant. Cells carrying such
[CTR+] aggregates showed increased sensitivity
to oxidative stress, and this phenotype could be transmitted to aggregate-free
[ctr-] cells by transformation with
[CTR+] cell extracts. Moreover, this
[CTR+] phenotype was inherited in a
non-Mendelian manner following mating with naïve
[ctr-] cells, but intriguingly the
[CTR+] phenotype was not eliminated by
guanidine-hydrochloride treatment. Thus, Ctr4 exhibits multiple features
diagnostic of other fungal prions and is the first example of a prion in fission
yeast. These findings suggest that transmissible protein-based determinants of
traits may be more widespread among fungi.
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Affiliation(s)
- Theodora Sideri
- University College London, Research Department of Genetics, Evolution & Environment and Institute of Healthy Ageing, London, U.K
| | - Yoko Yashiroda
- Chemical Genetics Laboratory, RIKEN and Chemical Genomics Research Group, RIKEN CSRS, Saitama, Japan
| | - David A Ellis
- University College London, Research Department of Genetics, Evolution & Environment and Institute of Healthy Ageing, London, U.K
| | - María Rodríguez-López
- University College London, Research Department of Genetics, Evolution & Environment and Institute of Healthy Ageing, London, U.K
| | - Minoru Yoshida
- Chemical Genetics Laboratory, RIKEN and Chemical Genomics Research Group, RIKEN CSRS, Saitama, Japan
| | - Mick F Tuite
- Kent Fungal Group, University of Kent, School of Biosciences, Canterbury, Kent, U.K
| | - Jürg Bähler
- University College London, Research Department of Genetics, Evolution & Environment and Institute of Healthy Ageing, London, U.K
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Tikhodeyev ON, Tarasov OV, Bondarev SA. Allelic variants of hereditary prions: The bimodularity principle. Prion 2017; 11:4-24. [PMID: 28281926 PMCID: PMC5360123 DOI: 10.1080/19336896.2017.1283463] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 01/04/2017] [Accepted: 01/10/2017] [Indexed: 12/26/2022] Open
Abstract
Modern biology requires modern genetic concepts equally valid for all discovered mechanisms of inheritance, either "canonical" (mediated by DNA sequences) or epigenetic. Applying basic genetic terms such as "gene" and "allele" to protein hereditary factors is one of the necessary steps toward these concepts. The basic idea that different variants of the same prion protein can be considered as alleles has been previously proposed by Chernoff and Tuite. In this paper, the notion of prion allele is further developed. We propose the idea that any prion allele is a bimodular hereditary system that depends on a certain DNA sequence (DNA determinant) and a certain epigenetic mark (epigenetic determinant). Alteration of any of these 2 determinants may lead to establishment of a new prion allele. The bimodularity principle is valid not only for hereditary prions; it seems to be universal for any epigenetic hereditary factor.
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Affiliation(s)
- Oleg N. Tikhodeyev
- Department of Genetics & Biotechnology, Saint-Petersburg State University, Saint-Petersburg, Russia
| | - Oleg V. Tarasov
- Department of Genetics & Biotechnology, Saint-Petersburg State University, Saint-Petersburg, Russia
- Saint-Petersburg Scientific Center of RAS, Saint-Petersburg, Russia
| | - Stanislav A. Bondarev
- Department of Genetics & Biotechnology, Saint-Petersburg State University, Saint-Petersburg, Russia
- The Laboratory of Amyloid Biology, Saint-Petersburg State University, Saint-Petersburg, Russia
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18
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Abstract
Although prions were first discovered through their link to severe brain degenerative diseases in animals, the emergence of prions as regulators of the phenotype of the yeast Saccharomyces cerevisiae and the filamentous fungus Podospora anserina has revealed a new facet of prion biology. In most cases, fungal prions are carried without apparent detriment to the host cell, representing a novel form of epigenetic inheritance. This raises the question of whether or not yeast prions are beneficial survival factors or actually gives rise to a "disease state" that is selected against in nature. To date, most studies on the impact of fungal prions have focused on laboratory-cultivated "domesticated" strains of S. cerevisiae. At least eight prions have now been described in this species, each with the potential to impact on a wide range of cellular processes. The discovery of prions in nondomesticated strains of S. cerevisiae and P. anserina has confirmed that prions are not simply an artifact of "domestication" of this species. In this review, I describe what we currently know about the phenotypic impact of fungal prions. I then describe how the interplay between host genotype and the prion-mediated changes can generate a wide array of phenotypic diversity. How such prion-generated diversity may be of benefit to the host in survival in a fluctuating, often hazardous environment is then outlined. Prion research has now entered a new phase in which we must now consider their biological function and evolutionary significance in the natural world.
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Affiliation(s)
- Mick F Tuite
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom.
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19
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Abstract
The yeast Saccharomyces cerevisiae has emerged as an ideal model system to study the dynamics of prion proteins which are responsible for a number of fatal neurodegenerative diseases in humans. Within an infected cell, prion proteins aggregate in complexes which may increase in size or be fragmented and are transmitted upon cell division. Recent work in yeast suggests that only aggregates below a critical size are transmitted efficiently. We formulate a continuous-time branching process model of a yeast colony under conditions of prion curing. We generalize previous approaches by providing an explicit formula approximating prion loss as influenced by both aggregate growth and size-dependent transmission.
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20
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Yeast prions: Paramutation at the protein level? Semin Cell Dev Biol 2015; 44:51-61. [DOI: 10.1016/j.semcdb.2015.08.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 08/18/2015] [Indexed: 11/20/2022]
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21
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Reidy M, Masison DC. Yeast prions help identify and define chaperone interaction networks. Curr Pharm Biotechnol 2015; 15:1008-18. [PMID: 25373385 DOI: 10.2174/1389201015666141103021035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 07/22/2014] [Accepted: 10/05/2014] [Indexed: 11/22/2022]
Abstract
Proteins in the cell experience various stressful conditions that can affect their ability to attain and maintain the structural conformations they need to perform effectively. Protein chaperones are an important part of a cellular protein quality control system that protects the integrity of the proteome in the face of such challenges. Chaperones from different conserved families have multiple members that cooperate to regulate each other's activity and produce machines that perform a variety of tasks. The large numbers of related chaperones with both functionally overlapping and distinct activities allows fine-tuning of the machinery for specific tasks, but presents a daunting degree of complexity. Yeast prions are misfolded forms of cellular proteins whose propagation depends on the action of protein chaperones. Studying how propagation of yeast prions is affected by alterations in functions of various chaperones provides an approach to understanding this complexity.
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Affiliation(s)
| | - Daniel C Masison
- Building 8, Room 225, 8 Center Drive, Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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22
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Reidy M, Sharma R, Shastry S, Roberts BL, Albino-Flores I, Wickner S, Masison DC. Hsp40s specify functions of Hsp104 and Hsp90 protein chaperone machines. PLoS Genet 2014; 10:e1004720. [PMID: 25329162 PMCID: PMC4199505 DOI: 10.1371/journal.pgen.1004720] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 08/29/2014] [Indexed: 12/21/2022] Open
Abstract
Hsp100 family chaperones of microorganisms and plants cooperate with the Hsp70/Hsp40/NEF system to resolubilize and reactivate stress-denatured proteins. In yeast this machinery also promotes propagation of prions by fragmenting prion polymers. We previously showed the bacterial Hsp100 machinery cooperates with the yeast Hsp40 Ydj1 to support yeast thermotolerance and with the yeast Hsp40 Sis1 to propagate [PSI+] prions. Here we find these Hsp40s similarly directed specific activities of the yeast Hsp104-based machinery. By assessing the ability of Ydj1-Sis1 hybrid proteins to complement Ydj1 and Sis1 functions we show their C-terminal substrate-binding domains determined distinctions in these and other cellular functions of Ydj1 and Sis1. We find propagation of [URE3] prions was acutely sensitive to alterations in Sis1 activity, while that of [PIN+] prions was less sensitive than [URE3], but more sensitive than [PSI+]. These findings support the ideas that overexpressing Ydj1 cures [URE3] by competing with Sis1 for interaction with the Hsp104-based disaggregation machine, and that different prions rely differently on activity of this machinery, which can explain the various ways they respond to alterations in chaperone function. The cellular chaperone machinery helps proteins adopt and maintain native conformations and protects cells from stress. The yeast Hsp40s Ydj1 and Sis1 are co-chaperones that regulate Hsp70s, which are key components of many chaperone complexes. Both of these Hsp40s are crucial for growth and Ydj1 directs disaggregation activity of the Hsp100-based machinery to provide stress protection while Sis1 directs this activity to promote prion replication. Ydj1 also cures yeast of certain prions when overexpressed. We show that C-terminal domains that possess substrate-binding function of Ydj1 and Sis1 can mediate these and other functional distinctions and that the degree that prions depend on Sis1 activities could underlie differences in how they respond to alterations of chaperones. These findings support a view that Hsp40s regulate and specify functions of the chaperone machinery through substrate discrimination and cooperation with Hsp70. The disproportionate evolutionary expansion of Hsp40s (J-proteins) relative to their Hsp70 partners led to a proposal that this amplification allows increased regulation and fine-tuning of chaperone machines for increasingly complex processes. Our findings support this idea and provide insight into fundamental aspects of this cooperation.
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Affiliation(s)
- Michael Reidy
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, United States of America
| | - Ruchika Sharma
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, United States of America
| | - Shankar Shastry
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Brittany-Lee Roberts
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, United States of America
| | - Ivan Albino-Flores
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, United States of America
| | - Sue Wickner
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Daniel C. Masison
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, United States of America
- * E-mail:
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23
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Xue WF, Radford SE. An imaging and systems modeling approach to fibril breakage enables prediction of amyloid behavior. Biophys J 2014; 105:2811-9. [PMID: 24359753 DOI: 10.1016/j.bpj.2013.10.034] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 10/16/2013] [Accepted: 10/29/2013] [Indexed: 12/01/2022] Open
Abstract
Delineating the nanoscale properties and the dynamic assembly and disassembly behaviors of amyloid fibrils is key for technological applications that use the material properties of amyloid fibrils, as well as for developing treatments of amyloid-associated disease. However, quantitative mechanistic understanding of the complex processes involving these heterogeneous supramolecular systems presents challenges that have yet to be resolved. Here, we develop an approach that is capable of resolving the time dependence of fibril particle concentration, length distribution, and length and position dependence of fibril fragmentation rates using a generic mathematical framework combined with experimental data derived from atomic force microscopy analysis of fibril length distributions. By application to amyloid assembly of β2-microglobulin in vitro under constant mechanical stirring, we present a full description of the fibril fragmentation and growth behavior, and demonstrate the predictive power of the approach in terms of the samples' fibril dimensions, fibril load, and their efficiency to seed the growth of new amyloid fibrils. The approach developed offers opportunities to determine, quantify, and predict the course and the consequences of amyloid assembly.
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Affiliation(s)
- Wei-Feng Xue
- School of Biosciences, University of Kent, Canterbury, United Kingdom; Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom.
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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24
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Functional diversification of hsp40: distinct j-protein functional requirements for two prions allow for chaperone-dependent prion selection. PLoS Genet 2014; 10:e1004510. [PMID: 25058638 PMCID: PMC4109904 DOI: 10.1371/journal.pgen.1004510] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 05/30/2014] [Indexed: 01/22/2023] Open
Abstract
Yeast prions are heritable amyloid aggregates of functional yeast proteins; their propagation to subsequent cell generations is dependent upon fragmentation of prion protein aggregates by molecular chaperone proteins. Mounting evidence indicates the J-protein Sis1 may act as an amyloid specificity factor, recognizing prion and other amyloid aggregates and enabling Ssa and Hsp104 to act in prion fragmentation. Chaperone interactions with prions, however, can be affected by variations in amyloid-core structure resulting in distinct prion variants or ‘strains’. Our genetic analysis revealed that Sis1 domain requirements by distinct variants of [PSI+] are strongly dependent upon overall variant stability. Notably, multiple strong [PSI+] variants can be maintained by a minimal construct of Sis1 consisting of only the J-domain and glycine/phenylalanine-rich (G/F) region that was previously shown to be sufficient for cell viability and [RNQ+] prion propagation. In contrast, weak [PSI+] variants are lost under the same conditions but maintained by the expression of an Sis1 construct that lacks only the G/F region and cannot support [RNQ+] propagation, revealing mutually exclusive requirements for Sis1 function between these two prions. Prion loss is not due to [PSI+]-dependent toxicity or dependent upon a particular yeast genetic background. These observations necessitate that Sis1 must have at least two distinct functional roles that individual prions differentially require for propagation and which are localized to the glycine-rich domains of the Sis1. Based on these distinctions, Sis1 plasmid-shuffling in a [PSI+]/[RNQ+] strain permitted J-protein-dependent prion selection for either prion. We also found that, despite an initial report to the contrary, the human homolog of Sis1, Hdj1, is capable of [PSI+] prion propagation in place of Sis1. This conservation of function is also prion-variant dependent, indicating that only one of the two Sis1-prion functions may have been maintained in eukaryotic chaperone evolution. Multiple neurodegenerative disorders such as Alzheimer's, Parkinson's and Creutzfeldt-Jakob disease are associated with the accumulation of fibrous protein aggregates collectively termed ‘amyloid.’ In the baker's yeast Saccharomyces cerevisiae, multiple proteins form intracellular amyloid aggregates known as yeast prions. Yeast prions minimally require a core set of chaperone proteins for stable propagation in yeast, including the J-protein Sis1, which appears to be required for the propagation of all yeast prions and functioning similarly in each case. Here we present evidence which challenges the notion of a universal function for Sis1 in prion propagation and asserts instead that Sis1's function in the maintenance of at least two prions, [RNQ+] and [PSI+], is distinct and mutually exclusive for some prion variants. We also find that the human homolog of Sis1, called Hdj1, has retained the ability to support some, but not all yeast prions, indicating a partial conservation of function. Because yeast chaperones have the ability to both bind and fragment amyloids in vivo, further investigations into these prion-specific properties of Sis1 and Hdj1 will likely lead to new insights into the biological management of protein misfolding.
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25
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Abstract
The yeast Saccharomyces cerevisiae has emerged as an ideal model system to study the dynamics of prion proteins which are responsible for a number of fatal neurodegenerative diseases in humans. Within an infected cell, prion proteins aggregate in complexes which may increase in size or be fragmented and are transmitted upon cell division. Recent work in yeast suggests that only aggregates below a critical size are transmitted efficiently. We formulate a continuous-time branching process model of a yeast colony under conditions of prion curing. We generalize previous approaches by providing an explicit formula approximating prion loss as influenced by both aggregate growth and size-dependent transmission.
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26
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Hsp104 overexpression cures Saccharomyces cerevisiae [PSI+] by causing dissolution of the prion seeds. EUKARYOTIC CELL 2014; 13:635-47. [PMID: 24632242 DOI: 10.1128/ec.00300-13] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The [PSI(+)] yeast prion is formed when Sup35 misfolds into amyloid aggregates. [PSI(+)], like other yeast prions, is dependent on the molecular chaperone Hsp104, which severs the prion seeds so that they pass on as the yeast cells divide. Surprisingly, however, overexpression of Hsp104 also cures [PSI(+)]. Several models have been proposed to explain this effect: inhibition of severing, asymmetric segregation of the seeds between mother and daughter cells, and dissolution of the prion seeds. First, we found that neither the kinetics of curing nor the heterogeneity in the distribution of the green fluorescent protein (GFP)-labeled Sup35 foci in partially cured yeast cells is compatible with Hsp104 overexpression curing [PSI(+)] by inhibiting severing. Second, we ruled out the asymmetric segregation model by showing that the extent of curing was essentially the same in mother and daughter cells and that the fluorescent foci did not distribute asymmetrically, but rather, there was marked loss of foci in both mother and daughter cells. These results suggest that Hsp104 overexpression cures [PSI(+)] by dissolution of the prion seeds in a two-step process. First, trimming of the prion seeds by Hsp104 reduces their size, and second, their amyloid core is eliminated, most likely by proteolysis.
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27
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Chernova TA, Wilkinson KD, Chernoff YO. Physiological and environmental control of yeast prions. FEMS Microbiol Rev 2013; 38:326-44. [PMID: 24236638 DOI: 10.1111/1574-6976.12053] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 11/08/2013] [Accepted: 11/10/2013] [Indexed: 11/30/2022] Open
Abstract
Prions are self-perpetuating protein isoforms that cause fatal and incurable neurodegenerative disease in mammals. Recent evidence indicates that a majority of human proteins involved in amyloid and neural inclusion disorders possess at least some prion properties. In lower eukaryotes, such as yeast, prions act as epigenetic elements, which increase phenotypic diversity by altering a range of cellular processes. While some yeast prions are clearly pathogenic, it is also postulated that prion formation could be beneficial in variable environmental conditions. Yeast and mammalian prions have similar molecular properties. Crucial cellular factors and conditions influencing prion formation and propagation were uncovered in the yeast models. Stress-related chaperones, protein quality control deposits, degradation pathways, and cytoskeletal networks control prion formation and propagation in yeast. Environmental stresses trigger prion formation and loss, supposedly acting via influencing intracellular concentrations of the prion-inducing proteins, and/or by localizing prionogenic proteins to the prion induction sites via heterologous ancillary helpers. Physiological and environmental modulation of yeast prions points to new opportunities for pharmacological intervention and/or prophylactic measures targeting general cellular systems rather than the properties of individual amyloids and prions.
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Affiliation(s)
- Tatiana A Chernova
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
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28
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Schizosaccharomyces pombe disaggregation machinery chaperones support Saccharomyces cerevisiae growth and prion propagation. EUKARYOTIC CELL 2013; 12:739-45. [PMID: 23504563 DOI: 10.1128/ec.00301-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hsp100 chaperones protect microorganisms and plants from environmental stress by cooperating with Hsp70 and its nucleotide exchange factor (NEF) and Hsp40 cochaperones to resolubilize proteins from aggregates. The Saccharomyces cerevisiae Hsp104 (Sc-Hsp104)-based disaggregation machinery also is essential for replication of amyloid-based prions. Escherichia coli ClpB can substitute for Hsp104 to propagate [PSI(+)] prions in yeast, but only if E. coli DnaK and GrpE (Hsp70 and NEF) are coexpressed. Here, we tested if the reported inability of Schizosaccharomyces pombe Hsp104 (Sp-Hsp104) to support [PSI(+)] propagation was due to similar species-specific chaperone requirements and find that Sp-Hsp104 alone supported propagation of three different yeast prions. Sp-Hsp70 and Sp-Fes1p (NEF) likewise functioned in place of their Sa. cerevisiae counterparts. Thus, chaperones of these long-diverged species possess conserved activities that function in processes essential for both cell growth and prion propagation, suggesting Sc. pombe can propagate its own prions. We show that curing by Hsp104 overexpression and inactivation can be distinguished and confirm the observation that, unlike Sc-Hsp104, Sp-Hsp104 cannot cure yeast of [PSI(+)] when it is overexpressed. These results are consistent with a view that mechanisms underlying prion replication and elimination are distinct.
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29
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Newby GA, Lindquist S. Blessings in disguise: biological benefits of prion-like mechanisms. Trends Cell Biol 2013; 23:251-9. [PMID: 23485338 DOI: 10.1016/j.tcb.2013.01.007] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 01/17/2013] [Accepted: 01/25/2013] [Indexed: 02/07/2023]
Abstract
Prions and amyloids are often associated with disease, but related mechanisms provide beneficial functions in nature. Prion-like mechanisms (PriLiMs) are found from bacteria to humans, where they alter the biological and physical properties of prion-like proteins. We have proposed that prions can serve as heritable bet-hedging devices for diversifying microbial phenotypes. Other, more dynamic proteinaceous complexes may be governed by similar self-templating conformational switches. Additional PriLiMs continue to be identified and many share features of self-templating protein structure (including amyloids) and dependence on chaperone proteins. Here, we discuss several PriLiMs and their functions, intending to spur discussion and collaboration on the subject of beneficial prion-like behaviors.
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Affiliation(s)
- Gregory A Newby
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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30
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Sindi SS, Olofsson P. A Discrete-Time Branching Process Model of Yeast Prion Curing Curves. MATHEMATICAL POPULATION STUDIES 2013; 20:1-13. [PMID: 30287982 PMCID: PMC6168217 DOI: 10.1080/08898480.2013.748566] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The infectious agent of many neurodegenerative disorders is thought to be aggregates of prion protein, which are transmitted between cells. Recent work in yeast supports this hypothesis, but suggests that only aggregates below a critical size are transmitted efficiently. The total number of transmissible aggregates in a typical cell is a key determinant of strain infectivity. In a discrete-time branching process model of a yeast colony with prions, prion aggregates increase in size according to a Poisson process and only aggregates below a threshold size are transmitted during cell division. The total number of cells with aggregates in a growing population of yeast is expressed.
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31
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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.
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Affiliation(s)
- Susan W Liebman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557, USA.
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32
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Helsen CW, Glover JR. A new perspective on Hsp104-mediated propagation and curing of the yeast prion [PSI (+) ]. Prion 2012; 6:234-9. [PMID: 22561166 DOI: 10.4161/pri.19913] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Most prions in yeast form amyloid fibrils that must be severed by the protein disaggregase Hsp104 to be propagated and transmitted efficiently to newly formed buds. Only one yeast prion, [PSI (+) ], is cured by Hsp104 overexpression. We investigated the interaction between Hsp104 and Sup35, the priongenic protein in yeast that forms the [PSI (+) ] prion.1 We found that a 20-amino acid segment within the highly-charged, unstructured middle domain of Sup35 contributes to the physical interaction between the middle domain and Hsp104. When this segment was deleted from Sup35, the efficiency of [PSI (+) ] severing was substantially reduced, resulting in larger Sup35 particles and weakening of the [PSI (+) ] phenotype. Furthermore, [PSI (+) ] in these cells was completely resistant to Hsp104 curing. The affinity of Hsp104 was considerably weaker than that of model Hsp104-binding proteins and peptides, implying that Sup35 prions are not ideal substrates for Hsp104-mediated remodeling. In light of this finding, we present a modified model of Hsp104-mediated [PSI (+) ] propagation and curing that requires only partial remodeling of Sup35 assembled into amyloid fibrils.
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33
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Tyedmers J. Patterns of [PSI (+) ] aggregation allow insights into cellular organization of yeast prion aggregates. Prion 2012; 6:191-200. [PMID: 22449721 DOI: 10.4161/pri.18986] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The yeast prion phenomenon is very widespread and mounting evidence suggests that it has an impact on cellular regulatory mechanisms related to phenotypic responses to changing environments. Studying the aggregation patterns of prion amyloids during different stages of the prion life cycle is a first key step to understand major principles of how and where cells generate, organize and turn-over prion aggregates. The induction of the [PSI (+) ] state involves the actin cytoskeleton and quality control compartments such as the Insoluble Protein Deposit (IPOD). An initially unstable transitional induction state can be visualized by overexpression of the prion determinant and displays characteristic large ring- and ribbon-shaped aggregates consisting of poorly fragmented bundles of very long prion fibrils. In the mature prion state, the aggregation pattern is characterized by highly fragmented, shorter prion fibrils that form aggregates, which can be visualized through tagging with fluorescent proteins. The number of aggregates formed varies, ranging from a single large aggregate at the IPOD to multiple smaller ones, depending on several parameters discussed. Aggregate units below the resolution of light microscopy that are detectable by fluorescence correlation spectroscopy are in equilibrium with larger aggregates in this stage and can mediate faithful inheritance of the prion state. Loss of the prion state is often characterized by reduced fragmentation of prion fibrils and fewer, larger aggregates.
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Affiliation(s)
- Jens Tyedmers
- Center for Molecular Biology of the University of Heidelberg (ZMBH, Heidelberg, Germany.
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34
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Park YN, Morales D, Rubinson EH, Masison D, Eisenberg E, Greene LE. Differences in the curing of [PSI+] prion by various methods of Hsp104 inactivation. PLoS One 2012; 7:e37692. [PMID: 22719845 PMCID: PMC3377701 DOI: 10.1371/journal.pone.0037692] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 04/27/2012] [Indexed: 11/25/2022] Open
Abstract
[PSI+] yeast, containing the misfolded amyloid conformation of Sup35 prion, is cured by inactivation of Hsp104. There has been controversy as to whether inactivation of Hsp104 by guanidine treatment or by overexpression of the dominant negative Hsp104 mutant, Hsp104-2KT, cures [PSI+] by the same mechanism– inhibition of the severing of the prion seeds. Using live cell imaging of Sup35-GFP, overexpression of Hsp104-2KT caused the foci to increase in size, then decrease in number, and finally disappear when the cells were cured, similar to that observed in cells cured by depletion of Hsp104. In contrast, guanidine initially caused an increase in foci size but then the foci disappeared before the cells were cured. By starving the yeast to make the foci visible in cells grown with guanidine, the number of cells with foci was found to correlate exactly with the number of [PSI+] cells, regardless of the curing method. Therefore, the fluorescent foci are the prion seeds required for maintenance of [PSI+] and inactivation of Hsp104 cures [PSI+] by preventing severing of the prion seeds. During curing with guanidine, the reduction in seed size is an Hsp104-dependent effect that cannot be explained by limited severing of the seeds. Instead, in the presence of guanidine, Hsp104 retains an activity that trims or reduces the size of the prion seeds by releasing Sup35 molecules that are unable to form new prion seeds. This Hsp104 activity may also occur in propagating yeast.
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Affiliation(s)
- Yang-Nim Park
- Laboratory of Cell Biology, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - David Morales
- Laboratory of Cell Biology, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Emily H. Rubinson
- Laboratory of Cell Biology, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Daniel Masison
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institute of Health, Bethesda, Maryland, United States of America
| | - Evan Eisenberg
- Laboratory of Cell Biology, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Lois E. Greene
- Laboratory of Cell Biology, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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35
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Staniforth GL, Tuite MF. Fungal prions. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 107:417-56. [PMID: 22482457 DOI: 10.1016/b978-0-12-385883-2.00007-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
For both mammalian and fungal prion proteins, conformational templating drives the phenomenon of protein-only infectivity. The conformational conversion of a protein to its transmissible prion state is associated with changes to host cellular physiology. In mammals, this change is synonymous with disease, whereas in fungi no notable detrimental effect on the host is typically observed. Instead, fungal prions can serve as epigenetic regulators of inheritance in the form of partial loss-of-function phenotypes. In the presence of environmental challenges, the prion state [PRION(+)], with its resource for phenotypic plasticity, can be associated with a growth advantage. The growing number of yeast proteins that can switch to a heritable [PRION(+)] form represents diverse and metabolically penetrating cellular functions, suggesting that the [PRION(+)] state in yeast is a functional one, albeit rarely found in nature. In this chapter, we introduce the biochemical and genetic properties of fungal prions, many of which are shared by the mammalian prion protein PrP, and then outline the major contributions that studies on fungal prions have made to prion biology.
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Affiliation(s)
- Gemma L Staniforth
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent, United Kingdom
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36
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Helsen CW, Glover JR. Insight into molecular basis of curing of [PSI+] prion by overexpression of 104-kDa heat shock protein (Hsp104). J Biol Chem 2011; 287:542-556. [PMID: 22081611 DOI: 10.1074/jbc.m111.302869] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Yeast prions are a powerful model for understanding the dynamics of protein aggregation associated with a number of human neurodegenerative disorders. The AAA+ protein disaggregase Hsp104 can sever the amyloid fibrils produced by yeast prions. This action results in the propagation of "seeds" that are transmitted to daughter cells during budding. Overexpression of Hsp104 eliminates the [PSI+] prion but not other prions. Using biochemical methods we identified Hsp104 binding sites in the highly charged middle domain of Sup35, the protein determinant of [PSI+]. Deletion of a short segment of the middle domain (amino acids 129-148) diminishes Hsp104 binding and strongly affects the ability of the middle domain to stimulate the ATPase activity of Hsp104. In yeast, [PSI+] maintained by Sup35 lacking this segment, like other prions, is propagated by Hsp104 but cannot be cured by Hsp104 overexpression. These results provide new insight into the enigmatic specificity of Hsp104-mediated curing of yeast prions and sheds light on the limitations of the ability of Hsp104 to eliminate aggregates produced by other aggregation-prone proteins.
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Affiliation(s)
- Christopher W Helsen
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - John R Glover
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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37
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Abstract
Prions are infectious, self-propagating protein conformations. [PSI+], [RNQ+] and [URE3] are well characterized prions in Saccharomyces cerevisiae and represent the aggregated states of the translation termination factor Sup35, a functionally unknown protein Rnq1, and a regulator of nitrogen metabolism Ure2, respectively. Overproduction of Sup35 induces the de novo appearance of the [PSI+] prion in [RNQ+] or [URE3] strain, but not in non-prion strain. However, [RNQ+] and [URE3] prions themselves, as well as overexpression of a mutant Rnq1 protein, Rnq1Δ100, and Lsm4, hamper the maintenance of [PSI+]. These findings point to a bipolar activity of [RNQ+], [URE3], Rnq1Δ100, and Lsm4, and probably other yeast prion proteins as well, for the fate of [PSI+] prion. Possible mechanisms underlying the apparent bipolar activity of yeast prions will be discussed.
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Affiliation(s)
- Hiroshi Kurahashi
- Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, Tokyo, Japan
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38
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Hines JK, Craig EA. The sensitive [SWI (+)] prion: new perspectives on yeast prion diversity. Prion 2011; 5:164-8. [PMID: 21811098 DOI: 10.4161/pri.5.3.16895] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Yeast prions are heritable protein-based genetic elements which rely on molecular chaperone proteins for stable transmission to cell progeny. Within the past few years, five new prions have been validated and 18 additional putative prions identified in Saccharomyces cerevisiae. The exploration of the physical and biological properties of these "nouveau prions" has begun to reveal the extent of prion diversity in yeast. We recently reported that one such prion, [SWI(+)], differs from the best studied, archetypal prion [PSI(+)] in several significant ways. ( 1) Notably, [SWI(+)] is highly sensitive to alterations in Hsp70 system chaperone activity and is lost upon growth at elevated temperatures. In that report we briefly noted a correlation amongst prions regarding amino acid composition, seed number and sensitivity to the activity of the Hsp70 chaperone system. Here we extend that analysis and put forth the idea that [SWI(+)] may be representative of a class of asparagine-rich yeast prions which also includes [URE3], [MOT3(+)] and [ISP(+)], distinct from the glutamine-rich prions such as [PSI(+)] and [RNQ(+)]. While much work remains, it is apparent that our understanding of the extent of the diversity of prion characteristics is in its infancy.
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Affiliation(s)
- Justin K Hines
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
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39
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Palmer KJ, Ridout MS, Morgan BJT. Kinetic models of guanidine hydrochloride-induced curing of the yeast [PSI+] prion. J Theor Biol 2011; 274:1-11. [PMID: 21184760 DOI: 10.1016/j.jtbi.2010.12.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 12/15/2010] [Accepted: 12/15/2010] [Indexed: 11/30/2022]
Abstract
A population of [PSI(+)] Saccharomyces cerevisiae cells can be cured of the [PSI(+)] prion by the addition of guanidine hydrochloride (GdnHCl). In this paper we extend existing nucleated polymerisation simulation models to investigate the mechanisms that might underlie curing. Our results are consistent with the belief that prions are dispersed through the cells at division following GdnHCl addition. A key feature of the simulation model is that the probability that a polymer is transmitted from mother to daughter during cell division is dependent upon the length of the polymer. The model is able to reproduce the essential features of data from several different experimental protocols involving addition and removal of GdnHCl.
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Affiliation(s)
- K J Palmer
- School of Mathematics, Statistics and Actuarial Science, University of Kent, Canterbury, Kent CT2 7NF, United Kingdom
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40
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DiSalvo S, Serio TR. Insights into prion biology: integrating a protein misfolding pathway with its cellular environment. Prion 2011; 5:76-83. [PMID: 21654204 DOI: 10.4161/pri.5.2.16413] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Protein misfolding and assembly into ordered, self-templating aggregates (amyloid) has emerged as a novel mechanism for regulating protein function. For a subclass of amyloidogenic proteins known as prions, this process induces transmissible changes in normal cellular physiology, ranging from neurodegenerative disease in animals and humans to new traits in fungi. The severity and stability of these altered phenotypic states can be attenuated by the conformation or amino-acid sequence of the prion, but in most of these cases, the protein retains the ability to form amyloid in vitro. Thus, our ability to link amyloid formation in vitro with its biological consequences in vivo remains a challenge. In two recent studies, we have begun to address this disconnect by assessing the effects of the cellular environment on traits associated with the misfolding of the yeast prion Sup35. Remarkably, the effects of quality control pathways and of limitations on protein transfer in vivo amplify the effects of even slight differences in the efficiency of Sup35 misfolding, leading to dramatic changes in the associated phenotype. Together, our studies suggest that the interplay between protein misfolding pathways and their cellular context is a crucial contributor to prion biology.
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Affiliation(s)
- Susanne DiSalvo
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, USA
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41
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Strain conformation, primary structure and the propagation of the yeast prion [PSI+]. Nat Struct Mol Biol 2011; 18:493-9. [PMID: 21423194 PMCID: PMC3490428 DOI: 10.1038/nsmb.2030] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 02/03/2011] [Indexed: 11/23/2022]
Abstract
Prion proteins can adopt multiple different infectious strain conformations. Here we examine how the sequence of a prion protein affects its capacity to propagate specific conformations by exploiting our ability to create two distinct infectious conformations of the yeast [PSI+] prion protein Sup35p, termed Sc4 and Sc37. PNM2, a Sup35p (G58D) point mutant originally identified for its dominant interference with prion propagation, leads to rapid, recessive loss of Sc4 but does not interfere with Sc37 propagation. PNM2 destabilizes the amyloid core of Sc37 causing compensatory effects that slow prion growth but aid prion division and result in robust Sc37 propagation. In contrast, PNM2 does not affect the structure or chaperone-mediated division of Sc4, but interferes with its delivery to daughter cells. Thus, effective delivery of infectious particles during cell division is a critical and conformation-dependent step in prion inheritance.
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42
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Hines JK, Li X, Du Z, Higurashi T, Li L, Craig EA. [SWI], the prion formed by the chromatin remodeling factor Swi1, is highly sensitive to alterations in Hsp70 chaperone system activity. PLoS Genet 2011; 7:e1001309. [PMID: 21379326 PMCID: PMC3040656 DOI: 10.1371/journal.pgen.1001309] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 01/12/2011] [Indexed: 11/24/2022] Open
Abstract
The yeast prion [SWI+], formed of heritable amyloid aggregates of the Swi1 protein, results in a partial loss of function of the SWI/SNF chromatin-remodeling complex, required for the regulation of a diverse set of genes. Our genetic analysis revealed that [SWI+] propagation is highly dependent upon the action of members of the Hsp70 molecular chaperone system, specifically the Hsp70 Ssa, two of its J-protein co-chaperones, Sis1 and Ydj1, and the nucleotide exchange factors of the Hsp110 family (Sse1/2). Notably, while all yeast prions tested thus far require Sis1, [SWI+] is the only one known to require the activity of Ydj1, the most abundant J-protein in yeast. The C-terminal region of Ydj1, which contains the client protein interaction domain, is required for [SWI+] propagation. However, Ydj1 is not unique in this regard, as another, closely related J-protein, Apj1, can substitute for it when expressed at a level approaching that of Ydj1. While dependent upon Ydj1 and Sis1 for propagation, [SWI+] is also highly sensitive to overexpression of both J-proteins. However, this increased prion-loss requires only the highly conserved 70 amino acid J-domain, which serves to stimulate the ATPase activity of Hsp70 and thus to stabilize its interaction with client protein. Overexpression of the J-domain from Sis1, Ydj1, or Apj1 is sufficient to destabilize [SWI+]. In addition, [SWI+] is lost upon overexpression of Sse nucleotide exchange factors, which act to destabilize Hsp70's interaction with client proteins. Given the plethora of genes affected by the activity of the SWI/SNF chromatin-remodeling complex, it is possible that this sensitivity of [SWI+] to the activity of Hsp70 chaperone machinery may serve a regulatory role, keeping this prion in an easily-lost, meta-stable state. Such sensitivity may provide a means to reach an optimal balance of phenotypic diversity within a cell population to better adapt to stressful environments. Yeast prions are heritable genetic elements, formed spontaneously by aggregation of a single protein. Prions can thus generate diverse phenotypes in a dominant, non-Mendelian fashion, without a corresponding change in chromosomal gene structure. Since the phenotypes caused by the presence of a prion are thought to affect the ability of cells to survive under different environmental conditions, those that have global effects on cell physiology are of particular interest. Here we report the results of a study of one such prion, [SWI+], formed by a component of the SWI/SNF chromatin-remodeling complex, which is required for the regulation of a diverse set of genes. We found that, compared to previously well-studied prions, [SWI+] is highly sensitive to changes in the activities of molecular chaperones, particularly components of the Hsp70 machinery. Both under- and over-expression of components of this system initiated rapid loss of the prion from the cell population. Since expression of molecular chaperones, often known as heat shock proteins, are known to vary under diverse environmental conditions, such “chaperone sensitivity” may allow alteration of traits that under particular environmental conditions convey a selective advantage and may be a common characteristic of prions formed from proteins involved in global gene regulation.
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Affiliation(s)
- Justin K. Hines
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Xiaomo Li
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Zhiqiang Du
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Takashi Higurashi
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Liming Li
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- * E-mail: (EAC); (LL)
| | - Elizabeth A. Craig
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- * E-mail: (EAC); (LL)
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43
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Tuite MF, Marchante R, Kushnirov V. Fungal prions: structure, function and propagation. Top Curr Chem (Cham) 2011; 305:257-98. [PMID: 21717344 DOI: 10.1007/128_2011_172] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Prions are not uniquely associated with rare fatal neurodegenerative diseases in the animal kingdom; prions are also found in fungi and in particular the yeast Saccharomyces cerevisiae. As with animal prions, fungal prions are proteins able to exist in one or more self-propagating alternative conformations, but show little primary sequence relationship with the mammalian prion protein PrP. Rather, fungal prions represent a relatively diverse collection of proteins that participate in key cellular processes such as transcription and translation. Upon switching to their prion form, these proteins can generate stable, sometimes beneficial, changes in the host cell phenotype. Much has already been learnt about prion structure, and propagation and de novo generation of the prion state through studies in yeast and these findings are reviewed here.
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Affiliation(s)
- Mick F Tuite
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK.
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44
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Abstract
Prions are infectious, self-propagating protein conformations. [PSI+], [RNQ+] and [URE3] are well characterized prions in Saccharomyces cerevisiae and represent the aggregated states of the translation termination factor Sup35, a functionally unknown protein Rnq1, and a regulator of nitrogen metabolism Ure2, respectively. Overproduction of Sup35 induces the de novo appearance of the [PSI+] prion in [RNQ+] or [URE3] strain, but not in non-prion strain. However, [RNQ+] and [URE3] prions themselves, as well as overexpression of a mutant Rnq1 protein, Rnq1Δ100, and Lsm4, hamper the maintenance of [PSI+]. These findings point to a bipolar activity of [RNQ+], [URE3], Rnq1Δ100, and Lsm4, and probably other yeast prion proteins as well, for the fate of [PSI+] prion. Possible mechanisms underlying the apparent bipolar activity of yeast prions will be discussed.
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Affiliation(s)
- Hiroshi Kurahashi
- Department of Basic Medical Sciences; Institute of Medical Science; University of Tokyo; Tokyo, Japan,Department of Neurochemistry; Tohoku University Graduate School of Medicine; Sendai, Japan
| | - Keita Oishi
- Department of Basic Medical Sciences; Institute of Medical Science; University of Tokyo; Tokyo, Japan
| | - Yoshikazu Nakamura
- Department of Basic Medical Sciences; Institute of Medical Science; University of Tokyo; Tokyo, Japan
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45
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Derdowski A, Sindi SS, Klaips CL, DiSalvo S, Serio TR. A size threshold limits prion transmission and establishes phenotypic diversity. Science 2010; 330:680-3. [PMID: 21030659 DOI: 10.1126/science.1197785] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
According to the prion hypothesis, atypical phenotypes arise when a prion protein adopts an alternative conformation and persist when that form assembles into self-replicating aggregates. Amyloid formation in vitro provides a model for this protein-misfolding pathway, but the mechanism by which this process interacts with the cellular environment to produce transmissible phenotypes is poorly understood. Using the yeast prion Sup35/[PSI(+)], we found that protein conformation determined the size distribution of aggregates through its interactions with a molecular chaperone. Shifts in this range created variations in aggregate abundance among cells because of a size threshold for transmission, and this heterogeneity, along with aggregate growth and fragmentation, induced age-dependent fluctuations in phenotype. Thus, prion conformations may specify phenotypes as population averages in a dynamic system.
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Affiliation(s)
- Aaron Derdowski
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, 185 Meeting Street, Post Office Box G-L2, Providence, RI 02912, USA
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46
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Fernández-Tresguerres ME, de la Espina SMD, Gasset-Rosa F, Giraldo R. A DNA-promoted amyloid proteinopathy in Escherichia coli. Mol Microbiol 2010; 77:1456-69. [PMID: 20662778 DOI: 10.1111/j.1365-2958.2010.07299.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Protein amyloids arise from the conformational conversion and assembly of a soluble protein into fibrilar aggregates with a crossed β-sheet backbone. Amyloid aggregates are able to replicate by acting as a template for the structural transformation and accretion of further protein molecules. In physicochemical terms, amyloids arguably constitute the simplest self-replicative macromolecular assemblies. Similarly to the mammalian proteins PrP and α-synuclein, the winged-helix dimerization (WH1) domain of the bacterial, plasmid-encoded protein RepA can assemble into amyloid fibres upon binding to DNA in vitro. Here we report that a hyper-amyloidogenic functional variant (A31V) of RepA, fused to a red fluorescent protein, causes an amyloid proteinopathy in Escherichia coli with the following features: (i) in the presence of multiple copies of the specific DNA sequence opsp, WH1(A31V) accumulates as cytoplasmatic inclusions segregated from the nucleoid; (ii) such aggregates are amyloid in nature; (iii) bacteria carrying the amyloid inclusions age, exhibiting a fivefold expanded generation time; (iv) before cytokinesis, small inclusions are assembled de novo and transferred to the daughter cells, in which transmission failures cure amyloidosis; and (v) in the absence of inducer DNA, purified cellular WH1(A31V) inclusions seed amyloid fibre growth in vitro from the soluble protein. RepA-WH1 is a suitable bacterial model system for amyloid proteinopathies.
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Affiliation(s)
- M Elena Fernández-Tresguerres
- Department of Chemical and Physical Biology, Centro de Investigaciones Biológicas - CSIC, C/Ramiro de Maeztu, 9, E-28040 Madrid, Spain
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47
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Grimminger-Marquardt V, Lashuel HA. Structure and function of the molecular chaperone Hsp104 from yeast. Biopolymers 2010; 93:252-76. [PMID: 19768774 DOI: 10.1002/bip.21301] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The molecular chaperone Hsp104 plays a central role in the clearance of aggregates after heat shock and the propagation of yeast prions. Hsp104's disaggregation activity and prion propagation have been linked to its ability to resolubilize or remodel protein aggregates. However, Hsp104 has also the capacity to catalyze protein aggregation of some substrates at specific conditions. Hence, it is a molecular chaperone with two opposing activities with respect to protein aggregation. In yeast models of Huntington's disease, Hsp104 is required for the aggregation and toxicity of polyglutamine (polyQ), but the expression of Hsp104 in cellular and animal models of Huntington's and Parkinson's disease protects against polyQ and alpha-synuclein toxicity. Therefore, elucidating the molecular determinants and mechanisms underlying the ability of Hsp104 to switch between these two activities is of critical importance for understanding its function and could provide insight into novel strategies aimed at preventing or reversing the formation of toxic protein aggregation in systemic and neurodegenerative protein misfolding diseases. Here, we present an overview of the current molecular models and hypotheses that have been proposed to explain the role of Hsp104 in modulating protein aggregation and prion propagation. The experimental approaches and the evidences presented so far in relation to these models are examined. Our primary objective is to offer a critical review that will inspire the use of novel techniques and the design of new experiments to proceed towards a qualitative and quantitative understanding of the molecular mechanisms underlying the multifunctional properties of Hsp104 in vivo.
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Affiliation(s)
- Valerie Grimminger-Marquardt
- Laboratory of Molecular Neurobiology and Neuroproteomics, Swiss Federal Institute of Technology Lausanne (EPFL), FSV-BMI AI 2137.1, Station 15, CH-1015 Lausanne, Switzerland
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48
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Sindi SS, Serio TR. Prion dynamics and the quest for the genetic determinant in protein-only inheritance. Curr Opin Microbiol 2009; 12:623-30. [PMID: 19864176 DOI: 10.1016/j.mib.2009.09.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 09/12/2009] [Accepted: 09/14/2009] [Indexed: 01/24/2023]
Abstract
According to the prion hypothesis, proteins may act in atypical roles as genetic elements of infectivity and inheritance by undergoing self-replicating changes in physical state. While the preponderance of evidence strongly supports this concept particularly in fungi, the detailed mechanisms by which distinct protein forms specify unique phenotypes are emerging concepts. A particularly active area of investigation is the molecular nature of the heritable species, which has been probed through genetic, biochemical, and cell biological experimentation as well as by mathematical modeling. Here, we suggest that these studies are converging to implicate small aggregates composed of prion-state conformers as the transmissible genetic determinants of protein-based phenotypes.
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Affiliation(s)
- Suzanne S Sindi
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, 185 Meeting St., Box G-L2, Providence, RI 02912, USA
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49
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Masison DC, Kirkland PA, Sharma D. Influence of Hsp70s and their regulators on yeast prion propagation. Prion 2009; 3:65-73. [PMID: 19556854 DOI: 10.4161/pri.3.2.9134] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Propagation of yeast prions requires normal abundance and activity of many protein chaperones. Central among them is Hsp70, a ubiquitous and essential chaperone involved in many diverse cellular processes that helps promote proper protein folding and acts as a critical component of several chaperone machines. Hsp70 is regulated by a large cohort of co-chaperones, whose effects on prions are likely mediated through Hsp70. Hsp104 is another chaperone, absent from mammalian cells, that resolubilizes proteins from aggregates. This activity, which minimally requires Hsp70 and its co-chaperone Hsp40, is essential for yeast prion replication. Although much is known about how yeast prions can be affected by altering protein chaperones, mechanistic explanations for these effects are uncertain. We discuss the variety of effects Hsp70 and its regulators have on different prions and how the effects might be due to the many ways chaperones interact with each other and with amyloid.
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Affiliation(s)
- Daniel C Masison
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0830, USA.
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