1
|
Acs-Szabo L, Papp LA, Miklos I. Understanding the molecular mechanisms of human diseases: the benefits of fission yeasts. MICROBIAL CELL (GRAZ, AUSTRIA) 2024; 11:288-311. [PMID: 39104724 PMCID: PMC11299203 DOI: 10.15698/mic2024.08.833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 07/04/2024] [Accepted: 07/10/2024] [Indexed: 08/07/2024]
Abstract
The role of model organisms such as yeasts in life science research is crucial. Although the baker's yeast (Saccharomyces cerevisiae) is the most popular model among yeasts, the contribution of the fission yeasts (Schizosaccharomyces) to life science is also indisputable. Since both types of yeasts share several thousands of common orthologous genes with humans, they provide a simple research platform to investigate many fundamental molecular mechanisms and functions, thereby contributing to the understanding of the background of human diseases. In this review, we would like to highlight the many advantages of fission yeasts over budding yeasts. The usefulness of fission yeasts in virus research is shown as an example, presenting the most important research results related to the Human Immunodeficiency Virus Type 1 (HIV-1) Vpr protein. Besides, the potential role of fission yeasts in the study of prion biology is also discussed. Furthermore, we are keen to promote the uprising model yeast Schizosaccharomyces japonicus, which is a dimorphic species in the fission yeast genus. We propose the hyphal growth of S. japonicus as an unusual opportunity as a model to study the invadopodia of human cancer cells since the two seemingly different cell types can be compared along fundamental features. Here we also collect the latest laboratory protocols and bioinformatics tools for the fission yeasts to highlight the many possibilities available to the research community. In addition, we present several limiting factors that everyone should be aware of when working with yeast models.
Collapse
Affiliation(s)
- Lajos Acs-Szabo
- Department of Genetics and Applied Microbiology, Faculty of Science and Technology, University of DebrecenDebrecen, 4032Hungary
| | - Laszlo Attila Papp
- Department of Genetics and Applied Microbiology, Faculty of Science and Technology, University of DebrecenDebrecen, 4032Hungary
| | - Ida Miklos
- Department of Genetics and Applied Microbiology, Faculty of Science and Technology, University of DebrecenDebrecen, 4032Hungary
| |
Collapse
|
2
|
Harari A, Zoltsman G, Levin T, Rosenzweig R. Hsp104 N-terminal domain interaction with substrates plays a regulatory role in protein disaggregation. FEBS J 2022; 289:5359-5377. [PMID: 35305079 PMCID: PMC9541529 DOI: 10.1111/febs.16441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 02/01/2022] [Accepted: 03/17/2022] [Indexed: 01/19/2023]
Abstract
Heat shock protein 104 (Hsp104) protein disaggregases are powerful molecular machines that harness the energy derived from ATP binding and hydrolysis to disaggregate a wide range of protein aggregates and amyloids, as well as to assist in yeast prion propagation. Little is known, however, about how Hsp104 chaperones recognize such a diversity of substrates, or indeed the contribution of the substrate‐binding N‐terminal domain (NTD) to Hsp104 function. Herein, we present a NMR spectroscopy study, which structurally characterizes the Hsp104 NTD‐substrate interaction. We show that the NTD includes a substrate‐binding groove that specifically recognizes exposed hydrophobic stretches in unfolded, misfolded, amyloid and prion substrates of Hsp104. In addition, we find that the NTD itself has chaperoning activities which help to protect the exposed hydrophobic regions of its substrates from further misfolding and aggregation, thereby priming them for threading through the Hsp104 central channel. We further demonstrate that mutations to this substrate‐binding groove abolish Hsp104 activation by client proteins and keep the chaperone in a partially inhibited state. The Hsp104 variant with these mutations also exhibited significantly reduced disaggregation activity and cell survival at extreme temperatures. Together, our findings provide both a detailed characterization of the NTD‐substrate complex and insight into the functional regulatory role of the NTD in protein disaggregation and yeast thermotolerance.
Collapse
Affiliation(s)
- Anna Harari
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Guy Zoltsman
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Tal Levin
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Rina Rosenzweig
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| |
Collapse
|
3
|
Lau Y, Oamen HP, Caudron F. Protein Phase Separation during Stress Adaptation and Cellular Memory. Cells 2020; 9:cells9051302. [PMID: 32456195 PMCID: PMC7291175 DOI: 10.3390/cells9051302] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/14/2020] [Accepted: 05/21/2020] [Indexed: 12/13/2022] Open
Abstract
Cells need to organise and regulate their biochemical processes both in space and time in order to adapt to their surrounding environment. Spatial organisation of cellular components is facilitated by a complex network of membrane bound organelles. Both the membrane composition and the intra-organellar content of these organelles can be specifically and temporally controlled by imposing gates, much like bouncers controlling entry into night-clubs. In addition, a new level of compartmentalisation has recently emerged as a fundamental principle of cellular organisation, the formation of membrane-less organelles. Many of these structures are dynamic, rapidly condensing or dissolving and are therefore ideally suited to be involved in emergency cellular adaptation to stresses. Remarkably, the same proteins have also the propensity to adopt self-perpetuating assemblies which properties fit the needs to encode cellular memory. Here, we review some of the principles of phase separation and the function of membrane-less organelles focusing particularly on their roles during stress response and cellular memory.
Collapse
|
4
|
Kumar S, Masison DC. Hsp70-nucleotide exchange factor (NEF) Fes1 has non-NEF roles in degradation of gluconeogenic enzymes and cell wall integrity. PLoS Genet 2019; 15:e1008219. [PMID: 31242183 PMCID: PMC6615629 DOI: 10.1371/journal.pgen.1008219] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 07/09/2019] [Accepted: 05/28/2019] [Indexed: 12/03/2022] Open
Abstract
Fes1 is a conserved armadillo repeat-containing Hsp70 nucleotide exchange factor important for growth at high temperature, proteasomal protein degradation and prion propagation. Depleting or mutating Fes1 induces a stress response and causes defects in these processes that are ascribed solely to disruption of Fes1 regulation of Hsp70. Here, we find Fes1 was essential for degradation of gluconeogenic enzymes by the vacuole import and degradation (Vid) pathway and for cell wall integrity (CWI), which is crucial for growth at high temperature. Unexpectedly, Fes1 mutants defective in physical or functional interaction with Hsp70 retained activities that support Vid and CWI. Fes1 and the Fes1 mutants bound to the Vid substrate Fbp1 in vitro and captured Slt2, a signaling kinase that regulates CWI, from cell lysates. Our data show that the armadillo domain of Fes1 binds proteins other than Hsp70, that Fes1 has important Hsp70-independent roles in the cell, and that major growth defects caused by depleting Fes1 are due to loss of these functions rather than to loss of Hsp70 regulation. We uncovered diverse functions of Fes1 beyond its defined role in regulating Hsp70, which points to possible multi-functionality among its conserved counterparts in other organisms or organelles. Fes1, a yeast homolog of human nucleotide exchange factor HspBP1, binds and regulates Hsp70, a universally conserved protein that helps maintain health of proteins in cells. Fes1 is believed to function only by helping Hsp70 release ADP and substrates and cells lacking Fes1 are sick. We find Fes1 is essential for protein degradation by a vacuolar pathway (Vid) and for cell wall integrity (CWI), and it interacts with a Vid substrate and a regulator of CWI. Fes1 mutants that cannot regulate Hsp70 can still support Vid and CWI, interact with proteins involved in these processes and restore cell health. Thus, Fes1 binds proteins other than Hsp70 and has important functions beyond regulating Hsp70 that are needed for optimal cell fitness.
Collapse
Affiliation(s)
- Shailesh Kumar
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, 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, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| |
Collapse
|
5
|
Dual Roles for Yeast Sti1/Hop in Regulating the Hsp90 Chaperone Cycle. Genetics 2018; 209:1139-1154. [PMID: 29930177 DOI: 10.1534/genetics.118.301178] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 06/20/2018] [Indexed: 11/18/2022] Open
Abstract
The Hsp90 chaperone is regulated by many cochaperones that tune its activities, but how they act to coordinate various steps in the reaction cycle is unclear. The primary role of Saccharomyces cerevisiae Hsp70/Hsp90 cochaperone Sti1 (Hop in mammals) is to bridge Hsp70 and Hsp90 to facilitate client transfer. Sti1 is not essential, so Hsp90 can interact with Hsp70 in vivo without Sti1. Nevertheless, many Hsp90 mutations make Sti1 necessary. We noted that Sti1-dependent mutations cluster in regions proximal to N-terminal domains (SdN) or C-terminal domains (SdC), which are known to be important for interaction with Hsp70 or clients, respectively. To uncover mechanistic details of Sti1-Hsp90 cooperation, we identified intramolecular suppressors of the Hsp90 mutants and assessed their physical, functional, and genetic interactions with Hsp70, Sti1, and other cochaperones. Our findings suggest Hsp90 SdN and SdC mutants depend on the same interaction with Sti1, but for different reasons. Sti1 promoted an essential Hsp70 interaction in the SdN region and supported SdC-region function by establishing an Hsp90 conformation crucial for capturing clients and progressing through the reaction cycle. We find the Hsp70 interaction and relationship with Sti1/Hop is conserved in the human Hsp90 system. Our work consolidates and clarifies much structural, biochemical, and computational data to define in vivo roles of Sti1/Hop in coordinating Hsp70 binding and client transfer with progression of the Hsp90 reaction cycle.
Collapse
|
6
|
Greene LE, Zhao X, Eisenberg E. Curing of [PSI +] by Hsp104 Overexpression: Clues to solving the puzzle. Prion 2018; 12:9-15. [PMID: 29227184 DOI: 10.1080/19336896.2017.1412911] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The yeast [PSI+] prion, which is the amyloid form of Sup35, has the unusual property of being cured not only by the inactivation of, but also by the overexpression of Hsp104. Even though this latter observation was made more than two decades ago, the mechanism of curing by Hsp104 overexpression has remained controversial. This question has been investigated in depth by our laboratory by combining live cell imaging of GFP-labeled Sup35 with standard plating assays of yeast overexpressing Hsp104. We will discuss why the curing of [PSI+] by Hsp104 overexpression is not compatible with a mechanism of either inhibition of severing of the prion seeds or asymmetric segregation of the seeds. Instead, our recent data (J. Biol. Chem. 292:8630-8641) indicate that curing is due to dissolution of the prion seeds, which in turn is dependent on the trimming activity of Hsp104. This trimming activity decreases the size of the seeds by dissociating monomers from the fibers, but unlike Hsp104 severing activity, it does not increase the number of prion seeds. Finally, we will discuss the other factors that affect the curing of [PSI+] by Hsp104 overexpression and how these factors may relate to the trimming activity of Hsp104.
Collapse
Affiliation(s)
- Lois E Greene
- a Laboratory of Cell Biology , NHLBI, NIH , Bethesda , MD , USA
| | - Xiaohong Zhao
- a Laboratory of Cell Biology , NHLBI, NIH , Bethesda , MD , USA
| | - Evan Eisenberg
- a Laboratory of Cell Biology , NHLBI, NIH , Bethesda , MD , USA
| |
Collapse
|
7
|
Zhao X, Rodriguez R, Silberman RE, Ahearn JM, Saidha S, Cummins KC, Eisenberg E, Greene LE. Heat shock protein 104 (Hsp104)-mediated curing of [ PSI+] yeast prions depends on both [ PSI+] conformation and the properties of the Hsp104 homologs. J Biol Chem 2017; 292:8630-8641. [PMID: 28373280 DOI: 10.1074/jbc.m116.770719] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 03/29/2017] [Indexed: 11/06/2022] Open
Abstract
Prions arise from proteins that have two possible conformations: properly folded and non-infectious or misfolded and infectious. The [PSI+] yeast prion, which is the misfolded and self-propagating form of the translation termination factor eRF3 (Sup35), can be cured of its infectious conformation by overexpression of Hsp104, which helps dissolve the prion seeds. This dissolution depends on the trimming activity of Hsp104, which reduces the size of the prion seeds without increasing their number. To further understand the relationship between trimming and curing, trimming was followed by measuring the loss of GFP-labeled Sup35 foci from both strong and weak [PSI+] variants; the former variant has more seeds and less soluble Sup35 than the latter. Overexpression of Saccharomyces cerevisiae Hsp104 (Sc-Hsp104) trimmed the weak [PSI+] variants much faster than the strong variants and cured the weak variants an order of magnitude faster than the strong variants. Overexpression of the fungal Hsp104 homologs from Schizosaccharomyces pombe (Sp-Hsp104) or Candida albicans (Ca-Hsp104) also trimmed and cured the weak variants, but interestingly, it neither trimmed nor cured the strong variants. These results show that, because Sc-Hsp104 has greater trimming activity than either Ca-Hsp104 or Sp-Hsp104, it cures both the weak and strong variants, whereas Ca-Hsp104 and Sp-Hsp104 only cure the weak variants. Therefore, curing by Hsp104 overexpression depends on both the trimming ability of the fungal Hsp104 homolog and the strength of the [PSI+] variant: the greater the trimming activity of the Hsp104 homolog and the weaker the variant, the greater the curing.
Collapse
Affiliation(s)
- Xiaohong Zhao
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| | - Ramon Rodriguez
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| | - Rebecca E Silberman
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| | - Joseph M Ahearn
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| | - Sheela Saidha
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| | - Kaelyn C Cummins
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| | - Evan Eisenberg
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| | - Lois E Greene
- From the Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-0301
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Wickner RB, Edskes HK, Gorkovskiy A, Bezsonov EE, Stroobant EE. Yeast and Fungal Prions: Amyloid-Handling Systems, Amyloid Structure, and Prion Biology. ADVANCES IN GENETICS 2016; 93:191-236. [PMID: 26915272 PMCID: PMC9432818 DOI: 10.1016/bs.adgen.2015.12.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Yeast prions (infectious proteins) were discovered by their outré genetic properties and have become important models for an array of human prion and amyloid diseases. A single prion protein can become any of many distinct amyloid forms (called prion variants or strains), each of which is self-propagating, but with different biological properties (eg, lethal vs mild). The folded in-register parallel β sheet architecture of the yeast prion amyloids naturally suggests a mechanism by which prion variant information can be faithfully transmitted for many generations. The yeast prions rely on cellular chaperones for their propagation, but can be cured by various chaperone imbalances. The Btn2/Cur1 system normally cures most variants of the [URE3] prion that arise. Although most variants of the [PSI+] and [URE3] prions are toxic or lethal, some are mild in their effects. Even the most mild forms of these prions are rare in the wild, indicating that they too are detrimental to yeast. The beneficial [Het-s] prion of Podospora anserina poses an important contrast in its structure, biology, and evolution to the yeast prions characterized thus far.
Collapse
Affiliation(s)
- R B Wickner
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - H K Edskes
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - A Gorkovskiy
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - E E Bezsonov
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - E E Stroobant
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| |
Collapse
|
10
|
Troisi EM, Rockman ME, Nguyen PP, Oliver EE, Hines JK. Swa2, the yeast homolog of mammalian auxilin, is specifically required for the propagation of the prion variant [URE3-1]. Mol Microbiol 2015; 97:926-41. [PMID: 26031938 PMCID: PMC4689296 DOI: 10.1111/mmi.13076] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2015] [Indexed: 01/09/2023]
Abstract
Yeast prions require a core set of chaperone proteins including Sis1, Hsp70 and Hsp104 to generate new amyloid templates for stable propagation, yet emerging studies indicate that propagation of some prions requires additional chaperone activities, demonstrating chaperone specificity beyond the common amyloid requirements. To comprehensively assess such prion-specific requirements for the propagation of the [URE3] prion variant [URE3-1], we screened 12 yeast cytosolic J-proteins, and here we report a novel role for the J-protein Swa2/Aux1. Swa2 is the sole yeast homolog of the mammalian protein auxilin, which, like Swa2, functions in vesicle-mediated endocytosis by disassembling the structural lattice formed by the protein clathrin. We found that, in addition to Sis1, [URE3-1] is specifically dependent upon Swa2, but not on any of the 11 other J-proteins. Further, we show that [URE3-1] propagation requires both a functional J-domain and the tetratricopeptide repeat (TPR) domain, but surprisingly does not require Swa2-clathrin binding. Because the J-domain of Swa2 can be replaced with the J-domains of other proteins, our data strongly suggest that prion-chaperone specificity arises from the Swa2 TPR domain and supports a model where Swa2 acts through Hsp70, most likely to provide additional access points for Hsp104 to promote prion template generation.
Collapse
Affiliation(s)
| | | | - Phil P Nguyen
- Department of Chemistry, Lafayette College, Easton, PA, USA
| | - Emily E Oliver
- Department of Chemistry, Lafayette College, Easton, PA, USA
| | - Justin K Hines
- Department of Chemistry, Lafayette College, Easton, PA, USA
| |
Collapse
|
11
|
Abstract
A prion is an infectious protein horizontally transmitting a disease or trait without a required nucleic acid. Yeast and fungal prions are nonchromosomal genes composed of protein, generally an altered form of a protein that catalyzes the same alteration of the protein. Yeast prions are thus transmitted both vertically (as genes composed of protein) and horizontally (as infectious proteins, or prions). Formation of amyloids (linear ordered β-sheet-rich protein aggregates with β-strands perpendicular to the long axis of the filament) underlies most yeast and fungal prions, and a single prion protein can have any of several distinct self-propagating amyloid forms with different biological properties (prion variants). Here we review the mechanism of faithful templating of protein conformation, the biological roles of these prions, and their interactions with cellular chaperones, the Btn2 and Cur1 aggregate-handling systems, and other cellular factors governing prion generation and propagation. Human amyloidoses include the PrP-based prion conditions and many other, more common amyloid-based diseases, several of which show prion-like features. Yeast prions increasingly are serving as models for the understanding and treatment of many mammalian amyloidoses. Patients with different clinical pictures of the same amyloidosis may be the equivalent of yeasts with different prion variants.
Collapse
|
12
|
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.
Collapse
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.
| |
Collapse
|
13
|
Abstract
A prion is an infectious protein horizontally transmitting a disease or trait without a required nucleic acid. Yeast and fungal prions are nonchromosomal genes composed of protein, generally an altered form of a protein that catalyzes the same alteration of the protein. Yeast prions are thus transmitted both vertically (as genes composed of protein) and horizontally (as infectious proteins, or prions). Formation of amyloids (linear ordered β-sheet-rich protein aggregates with β-strands perpendicular to the long axis of the filament) underlies most yeast and fungal prions, and a single prion protein can have any of several distinct self-propagating amyloid forms with different biological properties (prion variants). Here we review the mechanism of faithful templating of protein conformation, the biological roles of these prions, and their interactions with cellular chaperones, the Btn2 and Cur1 aggregate-handling systems, and other cellular factors governing prion generation and propagation. Human amyloidoses include the PrP-based prion conditions and many other, more common amyloid-based diseases, several of which show prion-like features. Yeast prions increasingly are serving as models for the understanding and treatment of many mammalian amyloidoses. Patients with different clinical pictures of the same amyloidosis may be the equivalent of yeasts with different prion variants.
Collapse
|
14
|
Dicer and Hsp104 function in a negative feedback loop to confer robustness to environmental stress. Cell Rep 2014; 10:47-61. [PMID: 25543137 DOI: 10.1016/j.celrep.2014.12.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 11/06/2014] [Accepted: 12/02/2014] [Indexed: 11/22/2022] Open
Abstract
Epigenetic mechanisms can be influenced by environmental cues and thus evoke phenotypic variation. This plasticity can be advantageous for adaptation but also detrimental if not tightly controlled. Although having attracted considerable interest, it remains largely unknown if and how environmental cues such as temperature trigger epigenetic alterations. Using fission yeast, we demonstrate that environmentally induced discontinuous phenotypic variation is buffered by a negative feedback loop that involves the RNase Dicer and the protein disaggregase Hsp104. In the absence of Hsp104, Dicer accumulates in cytoplasmic inclusions and heterochromatin becomes unstable at elevated temperatures, an epigenetic state inherited for many cell divisions after the heat stress. Loss of Dicer leads to toxic aggregation of an exogenous prionogenic protein. Our results highlight the importance of feedback regulation in building epigenetic memory and uncover Hsp104 and Dicer as homeostatic controllers that buffer environmentally induced stochastic epigenetic variation and toxic aggregation of prionogenic proteins.
Collapse
|
15
|
Abstract
Sup35p of Saccharomyces cerevisiae can form the [PSI+] prion, an infectious amyloid in which the protein is largely inactive. The part of Sup35p that forms the amyloid is the region normally involved in control of mRNA turnover. The formation of [PSI+] by Sup35p's from other yeasts has been interpreted to imply that the prion-forming ability of Sup35p is conserved in evolution, and thus of survival/fitness/evolutionary value to these organisms. We surveyed a larger number of yeast and fungal species by the same criteria as used previously and find that the Sup35p from many species cannot form prions. [PSI+] could be formed by the Sup35p from Candida albicans, Candida maltosa, Debaromyces hansenii, and Kluyveromyces lactis, but orders of magnitude less often than the S. cerevisiae Sup35p converts to the prion form. The Sup35s from Schizosaccharomyces pombe and Ashbya gossypii clearly do not form [PSI+]. We were also unable to detect [PSI+] formation by the Sup35ps from Aspergillus nidulans, Aspergillus fumigatus, Magnaporthe grisea, Ustilago maydis, or Cryptococcus neoformans. Each of two C. albicans SUP35 alleles can form [PSI+], but transmission from one to the other is partially blocked. These results suggest that the prion-forming ability of Sup35p is not a conserved trait, but is an occasional deleterious side effect of a protein domain conserved for another function.
Collapse
|