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Xiao H, Duo L, Zhen J, Wang H, Guo Z. Static and dynamic disorder in Aβ40 fibrils. Biochem Biophys Res Commun 2022; 610:107-112. [PMID: 35461071 DOI: 10.1016/j.bbrc.2022.04.036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/08/2022] [Indexed: 12/01/2022]
Abstract
Deposition of Aβ aggregates in the form of amyloid fibrils is a pathological hallmark of Alzheimer's disease. Understanding the structure and dynamics of Aβ fibrils is important for delineating the mechanism of Aβ aggregation and developing effective therapeutic strategies. Here we used site-directed spin labeling and EPR spectroscopy to study the Aβ40 fibril structure and dynamics. We obtained the EPR spectra of 40 spin-labeled Aβ40 fibril samples, with spin labeling coverage of the entire Aβ40 sequence. Analysis of the spin exchange interaction and spin label mobility using spectral simulations suggest that the strength of spin exchange interaction is primarily determined by static disorder in the Aβ40 fibrils. EPR data suggest that the entire Aβ40 sequence except residue D1 is highly ordered and the two hydrophobic regions at residues 17-20 and 31-36 show the lowest static disorder. Dynamic disorder is relatively constant across all reside positions, with residues 22 and 23 having the highest dynamic disorder. Comparison of the EPR data for Aβ40 and Aβ42 fibrils shows overall more ordered packing interactions in Aβ40 fibrils. Another noteworthy difference is the C-terminal residue, which has high static disorder in Aβ42 fibrils, but is ordered in Aβ40 fibrils. The higher static disorder in Aβ42 fibrils may lead to increased fragmentation, monomer dissociation, and structural defects, which may contribute to increased aggregation through secondary nucleation.
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Affiliation(s)
- Hui Xiao
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Lan Duo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - James Zhen
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Hongsu Wang
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA.
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2
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Innate immunity to prions: anti-prion systems turn a tsunami of prions into a slow drip. Curr Genet 2021; 67:833-847. [PMID: 34319422 DOI: 10.1007/s00294-021-01203-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/06/2021] [Accepted: 07/07/2021] [Indexed: 12/17/2022]
Abstract
The yeast prions (infectious proteins) [URE3] and [PSI+] are essentially non-functional (or even toxic) amyloid forms of Ure2p and Sup35p, whose normal function is in nitrogen catabolite repression and translation termination, respectively. Yeast has an array of systems working in normal cells that largely block infection with prions, block most prion formation, cure most nascent prions and mitigate the toxic effects of those prions that escape the first three types of systems. Here we review recent progress in defining these anti-prion systems, how they work and how they are regulated. Polymorphisms of the prion domains partially block infection with prions. Ribosome-associated chaperones ensure proper folding of nascent proteins, thus reducing [PSI+] prion formation and curing many [PSI+] variants that do form. Btn2p is a sequestering protein which gathers [URE3] amyloid filaments to one place in the cells so that the prion is often lost by progeny cells. Proteasome impairment produces massive overexpression of Btn2p and paralog Cur1p, resulting in [URE3] curing. Inversely, increased proteasome activity, by derepression of proteasome component gene transcription or by 60S ribosomal subunit gene mutation, prevents prion curing by Btn2p or Cur1p. The nonsense-mediated decay proteins (Upf1,2,3) cure many nascent [PSI+] variants by associating with Sup35p directly. Normal levels of the disaggregating chaperone Hsp104 can also cure many [PSI+] prion variants. By keeping the cellular levels of certain inositol polyphosphates / pyrophosphates low, Siw14p cures certain [PSI+] variants. It is hoped that exploration of the yeast innate immunity to prions will lead to discovery of similar systems in humans.
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3
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Liu EN, Park G, Nohara J, Guo Z. Effect of spin labelling on the aggregation kinetics of yeast prion protein Ure2. ROYAL SOCIETY OPEN SCIENCE 2021; 8:201747. [PMID: 33959337 PMCID: PMC8074925 DOI: 10.1098/rsos.201747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 02/10/2021] [Indexed: 06/12/2023]
Abstract
Amyloid formation is involved in a wide range of neurodegenerative diseases including Alzheimer's and prion diseases. Structural understanding of the amyloid is critical to delineate the mechanism of aggregation and its pathological spreading. Site-directed spin labelling has emerged as a powerful structural tool in the studies of amyloid structures and provided structural evidence for the parallel in-register β-sheet structure for a wide range of amyloid proteins. It is generally accepted that spin labelling does not disrupt the structure of the amyloid fibrils, the end product of protein aggregation. The effect on the rate of protein aggregation, however, has not been well characterized. Here, we employed a scanning mutagenesis approach to study the effect of spin labelling on the aggregation rate of 79 spin-labelled variants of the Ure2 prion domain. The aggregation of Ure2 protein is the basis of yeast prion [URE3]. We found that all spin-labelled Ure2 mutants aggregated within the experimental timeframe of 15 to 40 h. Among the 79 spin-labelled positions, only five residue sites (N23, N27, S33, I35 and G42) showed a dramatic delay in the aggregation rate as a result of spin labelling. These positions may be important for fibril nucleation, a rate-limiting step in aggregation. Importantly, spin labelling at most of the sites had a muted effect on Ure2 aggregation kinetics, showing a general tolerance of spin labelling in protein aggregation studies.
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Affiliation(s)
- Emilie N. Liu
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Giovanna Park
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Junsuke Nohara
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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4
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Yang J, Dear AJ, Yao QQ, Liu Z, Dobson CM, Knowles TPJ, Wu S, Perrett S. Amelioration of aggregate cytotoxicity by catalytic conversion of protein oligomers into amyloid fibrils. NANOSCALE 2020; 12:18663-18672. [PMID: 32794533 DOI: 10.1039/d0nr01481h] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The aggregation of peptides and proteins into amyloid fibrils is a molecular self-assembly phenomenon associated with both biological function and malfunction, notably in the context of neurodegenerative diseases. Oligomeric species formed early in the aggregation process are generally associated with cytotoxicity. Extrinsic molecules such as peptides have been found to influence amyloid formation kinetics and regulate this cellular process. Here, we use single-molecule FRET and bulk assays combined with global kinetic analysis to study quantitatively the effect of an 8-residue peptide (LQVNIGNR) on fibril formation by the yeast prion protein Ure2. This peptide, which is derived from a segment of the Ure2 prion domain, forms vesicular assemblies that accelerate fibril formation of Ure2 by promoting conformational conversion of oligomeric intermediates into fibrillar species in a catalytic manner. This reduces oligomer longevity and consequently ameliorates cytotoxicity. The LQVNIGNR peptide was found to accelerate fibril formation of unrelated proteins including Tau and α-Synuclein, suggesting a general ability to catalyse fibrillation. This study provides a general strategy for investigating the microscopic mechanism of extrinsic factors on amyloid aggregation. This approach can readily be applied to other amyloid systems and demonstrates that acceleration of oligomer conversion is a promising strategy to reduce amyloid toxicity.
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Affiliation(s)
- Jie Yang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China.
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5
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Wickner RB, Edskes HK, Son M, Wu S, Niznikiewicz M. How Do Yeast Cells Contend with Prions? Int J Mol Sci 2020; 21:ijms21134742. [PMID: 32635197 PMCID: PMC7369894 DOI: 10.3390/ijms21134742] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 06/26/2020] [Accepted: 06/30/2020] [Indexed: 12/11/2022] Open
Abstract
Infectious proteins (prions) include an array of human (mammalian) and yeast amyloid diseases in which a protein or peptide forms a linear β-sheet-rich filament, at least one functional amyloid prion, and two functional infectious proteins unrelated to amyloid. In Saccharomyces cerevisiae, at least eight anti-prion systems deal with pathogenic amyloid yeast prions by (1) blocking their generation (Ssb1,2, Ssz1, Zuo1), (2) curing most variants as they arise (Btn2, Cur1, Hsp104, Upf1,2,3, Siw14), and (3) limiting the pathogenicity of variants that do arise and propagate (Sis1, Lug1). Known mechanisms include facilitating proper folding of the prion protein (Ssb1,2, Ssz1, Zuo1), producing highly asymmetric segregation of prion filaments in mitosis (Btn2, Hsp104), competing with the amyloid filaments for prion protein monomers (Upf1,2,3), and regulation of levels of inositol polyphosphates (Siw14). It is hoped that the discovery of yeast anti-prion systems and elucidation of their mechanisms will facilitate finding analogous or homologous systems in humans, whose manipulation may be useful in treatment.
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Polymorphic Aβ42 fibrils adopt similar secondary structure but differ in cross-strand side chain stacking interactions within the same β-sheet. Sci Rep 2020; 10:5720. [PMID: 32235842 PMCID: PMC7109039 DOI: 10.1038/s41598-020-62181-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 03/10/2020] [Indexed: 12/20/2022] Open
Abstract
Formation of polymorphic amyloid fibrils is a common feature in neurodegenerative diseases involving protein aggregation. In Alzheimer’s disease, different fibril structures may be associated with different clinical sub-types. Structural basis of fibril polymorphism is thus important for understanding the role of amyloid fibrils in the pathogenesis and progression of these diseases. Here we studied two types of Aβ42 fibrils prepared under quiescent and agitated conditions. Quiescent Aβ42 fibrils adopt a long and twisted morphology, while agitated fibrils are short and straight, forming large bundles via lateral association. EPR studies of these two types of Aβ42 fibrils show that the secondary structure is similar in both fibril polymorphs. At the same time, agitated Aβ42 fibrils show stronger interactions between spin labels across the full range of the Aβ42 sequence, suggesting a more tightly packed structure. Our data suggest that cross-strand side chain packing interactions within the same β-sheet may play a critical role in the formation of polymorphic fibrils.
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Wang J, Park G, Lee YK, Nguyen M, San Fung T, Lin TY, Hsu F, Guo Z. Spin Label Scanning Reveals Likely Locations of β-Strands in the Amyloid Fibrils of the Ure2 Prion Domain. ACS OMEGA 2020; 5:5984-5993. [PMID: 32226879 PMCID: PMC7098000 DOI: 10.1021/acsomega.9b04358] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 02/28/2020] [Indexed: 06/10/2023]
Abstract
In yeast, the formation of Ure2 fibrils underlies the prion state [URE3], in which the yeast loses the ability to distinguish good nitrogen sources from bad ones. The Ure2 prion domain is both necessary and sufficient for the formation of amyloid fibrils. Understanding the structure of Ure2 fibrils is important for understanding the propagation not only of the [URE3] prion but also of other yeast prions whose prion domains share similar features, such as the enrichment of asparagine and glutamine residues. Here, we report a structural study of the amyloid fibrils formed by the Ure2 prion domain using site-directed spin labeling and electron paramagnetic resonance (EPR) spectroscopy. We completed a spin label scanning of all the residue positions between 2 and 80 of the Ure2 prion domain. The EPR data show that the Ure2 fibril core consists of residues 8-68 and adopts a parallel in-register β-sheet structure. Most of the residues show strong spin-exchange interactions, suggesting that there are only short turns and no long loops in the fibril core. Based on the strength of spin-exchange interactions, we determined the likely locations of the β-strands. EPR data also show that the C-terminal region of the Ure2 prion domain is more disordered than the N-terminal region. The roles of hydrophobic and charged residues are analyzed. Overall, the structure of Ure2 fibrils appears to involve a balance of stabilizing interactions, such as asparagine ladders, and destabilizing interactions, such as stacking of charged residues.
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8
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Wang H, Lee YK, Xue C, Guo Z. Site-specific structural order in Alzheimer's Aβ42 fibrils. ROYAL SOCIETY OPEN SCIENCE 2018; 5:180166. [PMID: 30109072 PMCID: PMC6083707 DOI: 10.1098/rsos.180166] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 05/31/2018] [Indexed: 05/27/2023]
Abstract
Deposition of amyloid fibrils is a pathological hallmark of Alzheimer's disease. Aβ42 is the major protein whose aggregation leads to the formation of these fibrils. Understanding the detailed structure of Aβ42 fibrils is of particular importance for delineating the mechanism of Aβ42 aggregation and developing specific amyloid-targeting drugs. Here, we use site-directed spin labelling and electron paramagnetic resonance spectroscopy to study the site-specific structural order at each and every residue position in Aβ42 fibrils. Strong interactions between spin labels indicate highly ordered protein backbone at the labelling site, while weak interactions suggest disordered local structure. Our results show that Aβ42 consists of five β-strands (residues 2-7, 10-13, 17-20, 31-36, 39-41), three turns (residues 7-8, 14-16, 37-38) and one ordered loop (residues 21-30). Spin labels introduced at β-strand sites show strong spin-spin interactions, while spin labels at turn or loop sites show weak interactions. However, residues 24, 25 and 28 also show strong interactions between spin labels, suggesting that the loop 21-30 is partly ordered. In the context of recent structural work using solid-state NMR and cryoEM, the site-specific structural order revealed in this study provides a different perspective on backbone and side chain dynamics of Aβ42 fibrils.
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Affiliation(s)
| | | | | | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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9
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Yang J, Dear AJ, Michaels TCT, Dobson CM, Knowles TPJ, Wu S, Perrett S. Direct Observation of Oligomerization by Single Molecule Fluorescence Reveals a Multistep Aggregation Mechanism for the Yeast Prion Protein Ure2. J Am Chem Soc 2018; 140:2493-2503. [PMID: 29357227 PMCID: PMC5880511 DOI: 10.1021/jacs.7b10439] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
![]()
The self-assembly of polypeptides
into amyloid structures is associated
with a range of increasingly prevalent neurodegenerative diseases
as well as with a select set of functional processes in biology. The
phenomenon of self-assembly results in species with dramatically different
sizes, from small oligomers to large fibrils; however, the kinetic
relationship between these species is challenging to characterize.
In the case of prion aggregates, these structures can self-replicate
and act as infectious agents. Here we use single molecule spectroscopy
to obtain quantitative information on the oligomer populations formed
during aggregation of the yeast prion protein Ure2. Global analysis
of the aggregation kinetics reveals the molecular mechanism underlying
oligomer formation and depletion. Quantitative characterization indicates
that the majority of Ure2 oligomers are relatively short-lived, and
their rate of dissociation is much higher than their rate of conversion
into growing fibrils. We identify an initial metastable oligomer,
which can subsequently convert into a structurally distinct oligomer,
which in turn converts into growing fibrils. We also show that fragmentation
is responsible for the autocatalytic self-replication of Ure2 fibrils,
but that preformed fibrils do not promote oligomer formation, indicating
that secondary nucleation of the type observed for peptides and proteins
associated with neurodegenerative disease does not occur at a significant
rate for Ure2. These results establish a framework for elucidating
the temporal and causal relationship between oligomers and larger
fibrillar species in amyloid forming systems, and provide insights
into why functional amyloid systems are not toxic to their host organisms.
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Affiliation(s)
- Jie Yang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , 15 Datun Road, Chaoyang District, Beijing 100101, China.,University of the Chinese Academy of Sciences , 19A Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Alexander J Dear
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Thomas C T Michaels
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom.,Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
| | - Christopher M Dobson
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Tuomas P J Knowles
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom.,Cavendish Laboratory , J J Thomson Avenue, Cambridge CB3 1HE, United Kingdom
| | - Si Wu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , 15 Datun Road, Chaoyang District, Beijing 100101, China.,University of the Chinese Academy of Sciences , 19A Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Sarah Perrett
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , 15 Datun Road, Chaoyang District, Beijing 100101, China.,University of the Chinese Academy of Sciences , 19A Yuquan Road, Shijingshan District, Beijing 100049, China
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10
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Xue C, Lin TY, Chang D, Guo Z. Thioflavin T as an amyloid dye: fibril quantification, optimal concentration and effect on aggregation. ROYAL SOCIETY OPEN SCIENCE 2017. [PMID: 28280572 DOI: 10.5061/dryad.b8c4r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Formation of amyloid fibrils underlies a wide range of human disorders, including Alzheimer's and prion diseases. The amyloid fibrils can be readily detected thanks to thioflavin T (ThT), a small molecule that gives strong fluorescence upon binding to amyloids. Using the amyloid fibrils of Aβ40 and Aβ42 involved in Alzheimer's disease, and of yeast prion protein Ure2, here we study three aspects of ThT binding to amyloids: quantification of amyloid fibrils using ThT, the optimal ThT concentration for monitoring amyloid formation and the effect of ThT on aggregation kinetics. We show that ThT fluorescence correlates linearly with amyloid concentration over ThT concentrations ranging from 0.2 to 500 µM. At a given amyloid concentration, the plot of ThT fluorescence versus ThT concentration exhibits a bell-shaped curve. The maximal fluorescence signal depends mostly on the total ThT concentration, rather than amyloid to ThT ratio. For the three proteins investigated, the maximal fluorescence is observed at ThT concentrations of 20-50 µM. Aggregation kinetics experiments in the presence of different ThT concentrations show that ThT has little effect on aggregation at concentrations of 20 µM or lower. ThT at concentrations of 50 µM or more could affect the shape of the aggregation curves, but this effect is protein-dependent and not universal.
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Affiliation(s)
- Christine Xue
- Department of Neurology, Brain Research Institute, Molecular Biology Institute , University of California , Los Angeles, CA 90095 , USA
| | - Tiffany Yuwen Lin
- Department of Neurology, Brain Research Institute, Molecular Biology Institute , University of California , Los Angeles, CA 90095 , USA
| | - Dennis Chang
- Department of Neurology, Brain Research Institute, Molecular Biology Institute , University of California , Los Angeles, CA 90095 , USA
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute , University of California , Los Angeles, CA 90095 , USA
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11
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Xue C, Lin TY, Chang D, Guo Z. Thioflavin T as an amyloid dye: fibril quantification, optimal concentration and effect on aggregation. ROYAL SOCIETY OPEN SCIENCE 2017; 4:160696. [PMID: 28280572 PMCID: PMC5319338 DOI: 10.1098/rsos.160696] [Citation(s) in RCA: 400] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 11/28/2016] [Indexed: 05/18/2023]
Abstract
Formation of amyloid fibrils underlies a wide range of human disorders, including Alzheimer's and prion diseases. The amyloid fibrils can be readily detected thanks to thioflavin T (ThT), a small molecule that gives strong fluorescence upon binding to amyloids. Using the amyloid fibrils of Aβ40 and Aβ42 involved in Alzheimer's disease, and of yeast prion protein Ure2, here we study three aspects of ThT binding to amyloids: quantification of amyloid fibrils using ThT, the optimal ThT concentration for monitoring amyloid formation and the effect of ThT on aggregation kinetics. We show that ThT fluorescence correlates linearly with amyloid concentration over ThT concentrations ranging from 0.2 to 500 µM. At a given amyloid concentration, the plot of ThT fluorescence versus ThT concentration exhibits a bell-shaped curve. The maximal fluorescence signal depends mostly on the total ThT concentration, rather than amyloid to ThT ratio. For the three proteins investigated, the maximal fluorescence is observed at ThT concentrations of 20-50 µM. Aggregation kinetics experiments in the presence of different ThT concentrations show that ThT has little effect on aggregation at concentrations of 20 µM or lower. ThT at concentrations of 50 µM or more could affect the shape of the aggregation curves, but this effect is protein-dependent and not universal.
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Affiliation(s)
| | | | | | - Zhefeng Guo
- Author for correspondence: Zhefeng Guo e-mail:
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12
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Gu L, Tran J, Jiang L, Guo Z. A new structural model of Alzheimer's Aβ42 fibrils based on electron paramagnetic resonance data and Rosetta modeling. J Struct Biol 2016; 194:61-7. [PMID: 26827680 DOI: 10.1016/j.jsb.2016.01.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/24/2016] [Accepted: 01/27/2016] [Indexed: 10/22/2022]
Abstract
Brain deposition of Aβ in the form of amyloid plaques is a pathological hallmark of Alzheimer's disease. There are two major species of Aβ in the brain: Aβ42 and Aβ40. Although Aβ40 is several-fold more abundant than Aβ42 in soluble form, Aβ42 is the major component of amyloid plaques. Structural knowledge of Aβ42 fibrils is important both for understanding the process of Aβ aggregation and for designing fibril-targeting drugs. Here we report site-specific structural information of Aβ42 fibrils at 22 residue positions based on electron paramagnetic resonance data. In combination with structure prediction program Rosetta, we modeled Aβ42 fibril structure at atomic resolution. Our Aβ42 fibril model consists of four parallel in-register β-sheets: βN (residues ∼7-13), β1 (residues ∼17-20), β2 (residues ∼32-36), and βC (residues 39-41). The region of β1-loop-β2 in Aβ42 fibrils adopts similar structure as that in Aβ40 fibrils. This is consistent with our cross seeding data that Aβ42 fibril seeds shortened the lag phase of Aβ40 fibrillization. On the other hand, Aβ42 fibrils contain a C-terminal β-arc-β motif with a special turn, termed "arc", at residues 37-38, which is absent in Aβ40 fibrils. Our results can explain both the higher aggregation propensity of Aβ42 and the importance of Aβ42 to Aβ40 ratio in the pathogenesis of Alzheimer's disease.
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Affiliation(s)
- Lei Gu
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Joyce Tran
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Lin Jiang
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA.
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13
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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 DOI: 10.1016/bs.adgen.2015.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [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.
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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
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14
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Daus ML. Techniques to elucidate the conformation of prions. World J Biol Chem 2015; 6:218-222. [PMID: 26322176 PMCID: PMC4549762 DOI: 10.4331/wjbc.v6.i3.218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 05/04/2015] [Accepted: 06/16/2015] [Indexed: 02/05/2023] Open
Abstract
Proteinaceous infectious particles (prions) are unique pathogens as they are devoid of any coding nucleic acid. Whilst it is assumed that prion disease is transmitted by a misfolded isoform of the cellular prion protein, the structural insight of prions is still vague and research for high resolution structural information of prions is still ongoing. In this review, techniques that may contribute to the clarification of the conformation of prions are presented and discussed.
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15
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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.
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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.
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Gu L, Liu C, Stroud JC, Ngo S, Jiang L, Guo Z. Antiparallel triple-strand architecture for prefibrillar Aβ42 oligomers. J Biol Chem 2014; 289:27300-27313. [PMID: 25118290 PMCID: PMC4175361 DOI: 10.1074/jbc.m114.569004] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 08/05/2014] [Indexed: 12/21/2022] Open
Abstract
Aβ42 oligomers play key roles in the pathogenesis of Alzheimer disease, but their structures remain elusive partly due to their transient nature. Here, we show that Aβ42 in a fusion construct can be trapped in a stable oligomer state, which recapitulates characteristics of prefibrillar Aβ42 oligomers and enables us to establish their detailed structures. Site-directed spin labeling and electron paramagnetic resonance studies provide structural restraints in terms of side chain mobility and intermolecular distances at all 42 residue positions. Using these restraints and other biophysical data, we present a novel atomic-level oligomer model. In our model, each Aβ42 protein forms a single β-sheet with three β-strands in an antiparallel arrangement. Each β-sheet consists of four Aβ42 molecules in a head-to-tail arrangement. Four β-sheets are packed together in a face-to-back fashion. The stacking of identical segments between different β-sheets within an oligomer suggests that prefibrillar oligomers may interconvert with fibrils via strand rotation, wherein β-strands undergo an ∼90° rotation along the strand direction. This work provides insights into rational design of therapeutics targeting the process of interconversion between toxic oligomers and non-toxic fibrils.
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Affiliation(s)
- Lei Gu
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095
| | - Cong Liu
- Departments of Chemistry and Biochemistry and Biological Chemistry, Howard Hughes Medical Institute, UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095,; Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 200032, China, and
| | - James C Stroud
- Department of Chemistry and Chemical Biology, Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131
| | - Sam Ngo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095
| | - Lin Jiang
- Departments of Chemistry and Biochemistry and Biological Chemistry, Howard Hughes Medical Institute, UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095.
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