51
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Nanoscale studies link amyloid maturity with polyglutamine diseases onset. Sci Rep 2016; 6:31155. [PMID: 27499269 PMCID: PMC4976327 DOI: 10.1038/srep31155] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 07/01/2016] [Indexed: 02/06/2023] Open
Abstract
The presence of expanded poly-glutamine (polyQ) repeats in proteins is directly linked to the pathogenesis of several neurodegenerative diseases, including Huntington’s disease. However, the molecular and structural basis underlying the increased toxicity of aggregates formed by proteins containing expanded polyQ repeats remain poorly understood, in part due to the size and morphological heterogeneity of the aggregates they form in vitro. To address this knowledge gap and technical limitations, we investigated the structural, mechanical and morphological properties of fibrillar aggregates at the single molecule and nanometer scale using the first exon of the Huntingtin protein as a model system (Exon1). Our findings demonstrate a direct correlation of the morphological and mechanical properties of Exon1 aggregates with their structural organization at the single aggregate and nanometric scale and provide novel insights into the molecular and structural basis of Huntingtin Exon1 aggregation and toxicity.
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52
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Vieweg S, Ansaloni A, Wang ZM, Warner JB, Lashuel HA. An Intein-based Strategy for the Production of Tag-free Huntingtin Exon 1 Proteins Enables New Insights into the Polyglutamine Dependence of Httex1 Aggregation and Fibril Formation. J Biol Chem 2016; 291:12074-86. [PMID: 27002149 PMCID: PMC4933259 DOI: 10.1074/jbc.m116.713982] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 03/18/2016] [Indexed: 12/25/2022] Open
Abstract
The first exon of the Huntingtin protein (Httex1) is one of the most actively studied Htt fragments because its overexpression in R6/2 transgenic mice has been shown to recapitulate several key features of Huntington disease. However, the majority of biophysical studies of Httex1 are based on assessing the structure and aggregation of fusion constructs where Httex1 is fused to large proteins, such as glutathione S-transferase, maltose-binding protein, or thioredoxin, or released in solution upon in situ cleavage of these proteins. Herein, we report an intein-based strategy that allows, for the first time, the rapid and efficient production of native tag-free Httex1 with polyQ repeats ranging from 7Q to 49Q. Aggregation studies on these proteins enabled us to identify interesting polyQ-length-dependent effects on Httex1 oligomer and fibril formation that were previously not observed using Httex1 fusion proteins or Httex1 proteins produced by in situ cleavage of fusion proteins. Our studies revealed the inability of Httex1-7Q/15Q to undergo amyloid fibril formation and an inverse correlation between fibril length and polyQ repeat length, suggesting possible polyQ length-dependent differences in the structural properties of the Httex1 aggregates. Altogether, our findings underscore the importance of working with tag-free Httex1 proteins and indicate that model systems based on non-native Httex1 sequences may not accurately reproduce the effect of polyQ repeat length and solution conditions on Httex1 aggregation kinetics and structural properties.
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Affiliation(s)
- Sophie Vieweg
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland and
| | - Annalisa Ansaloni
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland and
| | - Zhe-Ming Wang
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland and
| | - John B Warner
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland and
| | - Hilal A Lashuel
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland and Qatar Biomedical Research Institute (QBRI), Hamad bin Khalifa University (HBKU), 5825 Doha, Qatar
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53
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Arndt JR, Chaibva M, Legleiter J. The emerging role of the first 17 amino acids of huntingtin in Huntington's disease. Biomol Concepts 2016; 6:33-46. [PMID: 25741791 DOI: 10.1515/bmc-2015-0001] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 02/09/2015] [Indexed: 01/01/2023] Open
Abstract
Huntington's disease (HD) is caused by a polyglutamine (polyQ) domain that is expanded beyond a critical threshold near the N-terminus of the huntingtin (htt) protein, directly leading to htt aggregation. While full-length htt is a large (on the order of ∼350 kDa) protein, it is proteolyzed into a variety of N-terminal fragments that accumulate in oligomers, fibrils, and larger aggregates. It is clear that polyQ length is a key determinant of htt aggregation and toxicity. However, the flanking sequences around the polyQ domain, such as the first 17 amino acids on the N terminus (Nt17), influence aggregation, aggregate stability, influence other important biochemical properties of the protein and ultimately its role in pathogenesis. Here, we review the impact of Nt17 on htt aggregation mechanisms and kinetics, structural properties of Nt17 in both monomeric and aggregate forms, the potential role of posttranslational modifications (PTMs) that occur in Nt17 in HD, and the function of Nt17 as a membrane targeting domain.
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54
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Perevozchikova T, Stanley CB, McWilliams-Koeppen HP, Rowe EL, Berthelier V. Investigating the structural impact of the glutamine repeat in huntingtin assembly. Biophys J 2015; 107:411-421. [PMID: 25028883 DOI: 10.1016/j.bpj.2014.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 05/19/2014] [Accepted: 06/05/2014] [Indexed: 10/25/2022] Open
Abstract
Acquiring detailed structural information about the various aggregation states of the huntingtin-exon1 protein (Htt-exon1) is crucial not only for identifying the true nature of the neurotoxic species responsible for Huntington's disease (HD) but also for designing effective therapeutics. Using time-resolved small-angle neutron scattering (TR-SANS), we followed the conformational changes that occurred during fibrillization of the pathologic form of Htt-exon1 (NtQ42P10) and compared the results with those obtained for the wild-type (NtQ22P10). Our results show that the aggregation pathway of NtQ22P10 is very different from that of NtQ42P10, as the initial steps require a monomer to 7-mer transition stage. In contrast, the earliest species identified for NtQ42P10 are monomer and dimer. The divergent pathways ultimately result in NtQ22P10 fibrils that possess a packing arrangement consistent with the common amyloid sterical zipper model, whereas NtQ42P10 fibrils present a better fit to the Perutz β-helix structural model. The structural details obtained by TR-SANS should help to delineate the key mechanisms that underpin Htt-exon1 aggregation leading to HD.
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Affiliation(s)
- Tatiana Perevozchikova
- Department of Medicine, University of Tennessee Health Science Center-Graduate School of Medicine, Knoxville, Tennessee
| | - Christopher B Stanley
- Biology and Biomedical Sciences Group, Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
| | - Helen P McWilliams-Koeppen
- Department of Medicine, University of Tennessee Health Science Center-Graduate School of Medicine, Knoxville, Tennessee
| | - Erica L Rowe
- Department of Medicine, University of Tennessee Health Science Center-Graduate School of Medicine, Knoxville, Tennessee
| | - Valerie Berthelier
- Department of Medicine, University of Tennessee Health Science Center-Graduate School of Medicine, Knoxville, Tennessee.
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55
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Arndt JR, Kondalaji SG, Maurer MM, Parker A, Legleiter J, Valentine SJ. Huntingtin N-Terminal Monomeric and Multimeric Structures Destabilized by Covalent Modification of Heteroatomic Residues. Biochemistry 2015; 54:4285-96. [PMID: 26098795 DOI: 10.1021/acs.biochem.5b00478] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Early stage oligomer formation of the huntingtin protein may be driven by self-association of the 17-residue amphipathic α-helix at the protein's N-terminus (Nt17). Oligomeric structures have been implicated in neuronal toxicity and may represent important neurotoxic species in Huntington's disease. Therefore, a residue-specific structural characterization of Nt17 is crucial to understanding and potentially inhibiting oligomer formation. Native electrospray ion mobility spectrometry-mass spectrometry (IMS-MS) techniques and molecular dynamics simulations (MDS) have been applied to study coexisting monomer and multimer conformations of Nt17, independent of the remainder of huntingtin exon 1. MDS suggests gas-phase monomer ion structures comprise a helix-turn-coil configuration and a helix-extended-coil region. Elongated dimer species comprise partially helical monomers arranged in an antiparallel geometry. This stacked helical bundle may represent the earliest stages of Nt17-driven oligomer formation. Nt17 monomers and multimers have been further probed using diethylpyrocarbonate (DEPC). An N-terminal site (N-terminus of Threonine-3) and Lysine-6 are modified at higher DEPC concentrations, which led to the formation of an intermediate monomer structure. These modifications resulted in decreased extended monomer ion conformers, as well as a reduction in multimer formation. From the MDS experiments for the dimer ions, Lys6 residues in both monomer constituents interact with Ser16 and Glu12 residues on adjacent peptides; therefore, the decrease in multimer formation could result from disruption of these or similar interactions. This work provides a structurally selective model from which to study Nt17 self-association and provides critical insight toward Nt17 multimerization and, possibly, the early stages of huntingtin exon 1 aggregation.
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Affiliation(s)
- James R Arndt
- †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Samaneh Ghassabi Kondalaji
- †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Megan M Maurer
- †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Arlo Parker
- †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Justin Legleiter
- †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Stephen J Valentine
- †C. Eugene Bennett Department of Chemistry, ‡WVNano Safe Initiative, and §The Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, United States
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56
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Isas JM, Langen R, Siemer AB. Solid-State Nuclear Magnetic Resonance on the Static and Dynamic Domains of Huntingtin Exon-1 Fibrils. Biochemistry 2015; 54:3942-9. [PMID: 26020223 DOI: 10.1021/acs.biochem.5b00281] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Amyloid-like fibrils formed by huntingtin exon-1 (htt_ex1) are a hallmark of Huntington's disease (HD). The structure of these fibrils is unknown, and determining their structure is an important step toward understanding the misfolding processes that cause HD. In HD, a polyglutamine (polyQ) domain in htt_ex1 is expanded to a degree that it gains the ability to form aggregates comprising the core of the resulting fibrils. Despite the simplicity of this polyQ sequence, the structure of htt_ex1 fibrils has been difficult to determine. This study provides a detailed structural investigation of fibrils formed by htt_ex1 using solid-state nuclear magnetic resonance (NMR) spectroscopy. We show that the polyQ domain of htt_ex1 forms the static amyloid core similar to polyQ model peptides. The Gln residues of this domain exist in two distinct conformations that are found in separate domains or monomers but are relatively close in space. The rest of htt_ex1 is relatively dynamic on an NMR time scale, especially the proline-rich C-terminus, which we found to be in a polyproline II helical and random coil conformation. We observed a similar dynamic C-terminus in a soluble form of htt_ex1, indicating that the conformation of this part of htt_ex1 is not changed upon its aggregation into an amyloid fibril. From these data, we propose a bottlebrush model for the fibrils formed by htt_ex1. In this model, the polyQ domains form the center and the proline-rich domains the bristles of the bottlebrush.
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Affiliation(s)
- J Mario Isas
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Ansgar B Siemer
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
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57
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Arndt JR, Brown RJ, Burke KA, Legleiter J, Valentine SJ. Lysine residues in the N-terminal huntingtin amphipathic α-helix play a key role in peptide aggregation. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:117-126. [PMID: 25601683 DOI: 10.1002/jms.3504] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/27/2014] [Accepted: 09/05/2014] [Indexed: 06/04/2023]
Abstract
Huntington's disease is a genetic neurodegenerative disorder caused by an expansion in a polyglutamine domain near the N-terminus of the huntingtin (htt) protein that results in the formation of protein aggregates. Here, htt aggregate structure has been examined using hydrogen-deuterium exchange techniques coupled with tandem mass spectrometry. The focus of the study is on the 17-residue N-terminal flanking region of the peptide that has been shown to alter htt aggregation kinetics and morphology. A top-down sequencing strategy employing electron transfer dissociation is utilized to determine the location of accessible and protected hydrogens. In these experiments, peptides aggregate in a deuterium-rich solvent at neutral pH and are subsequently subjected to deuterium-hydrogen back-exchange followed by rapid quenching, disaggregation, and tandem mass spectrometry analysis. Electrospray ionization of the peptide solution produces the [M + 5H](5+) to [M + 10H](10+) charge states and reveals the presence of multiple peptide sequences differing by single glutamine residues. The [M + 7H](7+) to [M + 9](9+) charge states corresponding to the full peptide are used in the electron transfer dissociation analyses. Evidence for protected residues is observed in the 17-residue N-terminal tract and specifically points to lysine residues as potentially playing a significant role in htt aggregation.
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Affiliation(s)
- James R Arndt
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, 26506, USA
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58
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Fodale V, Kegulian NC, Verani M, Cariulo C, Azzollini L, Petricca L, Daldin M, Boggio R, Padova A, Kuhn R, Pacifici R, Macdonald D, Schoenfeld RC, Park H, Isas JM, Langen R, Weiss A, Caricasole A. Polyglutamine- and temperature-dependent conformational rigidity in mutant huntingtin revealed by immunoassays and circular dichroism spectroscopy. PLoS One 2014; 9:e112262. [PMID: 25464275 PMCID: PMC4251833 DOI: 10.1371/journal.pone.0112262] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 10/06/2014] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND In Huntington's disease, expansion of a CAG triplet repeat occurs in exon 1 of the huntingtin gene (HTT), resulting in a protein bearing>35 polyglutamine residues whose N-terminal fragments display a high propensity to misfold and aggregate. Recent data demonstrate that polyglutamine expansion results in conformational changes in the huntingtin protein (HTT), which likely influence its biological and biophysical properties. Developing assays to characterize and measure these conformational changes in isolated proteins and biological samples would advance the testing of novel therapeutic approaches aimed at correcting mutant HTT misfolding. Time-resolved Förster energy transfer (TR-FRET)-based assays represent high-throughput, homogeneous, sensitive immunoassays widely employed for the quantification of proteins of interest. TR-FRET is extremely sensitive to small distances and can therefore provide conformational information based on detection of exposure and relative position of epitopes present on the target protein as recognized by selective antibodies. We have previously reported TR-FRET assays to quantify HTT proteins based on the use of antibodies specific for different amino-terminal HTT epitopes. Here, we investigate the possibility of interrogating HTT protein conformation using these assays. METHODOLOGY/PRINCIPAL FINDINGS By performing TR-FRET measurements on the same samples (purified recombinant proteins or lysates from cells expressing HTT fragments or full length protein) at different temperatures, we have discovered a temperature-dependent, reversible, polyglutamine-dependent conformational change of wild type and expanded mutant HTT proteins. Circular dichroism spectroscopy confirms the temperature and polyglutamine-dependent change in HTT structure, revealing an effect of polyglutamine length and of temperature on the alpha-helical content of the protein. CONCLUSIONS/SIGNIFICANCE The temperature- and polyglutamine-dependent effects observed with TR-FRET on HTT proteins represent a simple, scalable, quantitative and sensitive assay to identify genetic and pharmacological modulators of mutant HTT conformation, and potentially to assess the relevance of conformational changes during onset and progression of Huntington's disease.
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Affiliation(s)
| | - Natalie C. Kegulian
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | | | | | | | | | | | | | | | | | - Robert Pacifici
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - Douglas Macdonald
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - Ryan C. Schoenfeld
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - Hyunsun Park
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - J. Mario Isas
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
- * E-mail: (RL); (AW); (AC)
| | - Andreas Weiss
- IRBM Promidis, Pomezia, Rome, Italy
- * E-mail: (RL); (AW); (AC)
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59
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Hoop CL, Lin HK, Kar K, Hou Z, Poirier MA, Wetzel R, van der Wel PCA. Polyglutamine amyloid core boundaries and flanking domain dynamics in huntingtin fragment fibrils determined by solid-state nuclear magnetic resonance. Biochemistry 2014; 53:6653-66. [PMID: 25280367 PMCID: PMC4211650 DOI: 10.1021/bi501010q] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
In Huntington’s disease, expansion
of a polyglutamine (polyQ)
domain in the huntingtin (htt) protein leads to misfolding and aggregation.
There is much interest in the molecular features that distinguish
monomeric, oligomeric, and fibrillar species that populate the aggregation
pathway and likely differ in cytotoxicity. The mechanism and rate
of aggregation are greatly affected by the domains flanking the polyQ
segment within exon 1 of htt. A “protective” C-terminal
proline-rich flanking domain inhibits aggregation by inducing polyproline
II structure (PPII) within an extended portion of polyQ. The N-terminal
flanking segment (httNT) adopts an α-helical structure
as it drives aggregation, helps stabilize oligomers and fibrils, and
is seemingly integral to their supramolecular assembly. Via solid-state
nuclear magnetic resonance (ssNMR), we probe how, in the mature fibrils,
the htt flanking domains impact the polyQ domain and in particular
the localization of the β-structured amyloid core. Using residue-specific
and uniformly labeled samples, we find that the amyloid core occupies
most of the polyQ domain but ends just prior to the prolines. We probe
the structural and dynamical features of the remarkably abrupt β-sheet
to PPII transition and discuss the potential connections to certain
htt-binding proteins. We also examine the httNT α-helix
outside the polyQ amyloid core. Despite its presumed structural and
demonstrated stabilizing roles in the fibrils, quantitative ssNMR
measurements of residue-specific dynamics show that it undergoes distinct
solvent-coupled motion. This dynamical feature seems reminiscent of
molten-globule-like α-helix-rich features attributed to the
nonfibrillar oligomeric species of various amyloidogenic proteins.
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Affiliation(s)
- Cody L Hoop
- Department of Structural Biology, University of Pittsburgh School of Medicine , Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States
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60
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Röthlein C, Miettinen MS, Borwankar T, Bürger J, Mielke T, Kumke MU, Ignatova Z. Architecture of polyglutamine-containing fibrils from time-resolved fluorescence decay. J Biol Chem 2014; 289:26817-26828. [PMID: 25092288 DOI: 10.1074/jbc.m114.581991] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The disease risk and age of onset of Huntington disease (HD) and nine other repeat disorders strongly depend on the expansion of CAG repeats encoding consecutive polyglutamines (polyQ) in the corresponding disease protein. PolyQ length-dependent misfolding and aggregation are the hallmarks of CAG pathologies. Despite intense effort, the overall structure of these aggregates remains poorly understood. Here, we used sensitive time-dependent fluorescent decay measurements to assess the architecture of mature fibrils of huntingtin (Htt) exon 1 implicated in HD pathology. Varying the position of the fluorescent labels in the Htt monomer with expanded 51Q (Htt51Q) and using structural models of putative fibril structures, we generated distance distributions between donors and acceptors covering all possible distances between the monomers or monomer dimensions within the polyQ amyloid fibril. Using Monte Carlo simulations, we systematically scanned all possible monomer conformations that fit the experimentally measured decay times. Monomers with four-stranded 51Q stretches organized into five-layered β-sheets with alternating N termini of the monomers perpendicular to the fibril axis gave the best fit to our data. Alternatively, the core structure of the polyQ fibrils might also be a zipper layer with antiparallel four-stranded stretches as this structure showed the next best fit. All other remaining arrangements are clearly excluded by the data. Furthermore, the assessed dimensions of the polyQ stretch of each monomer provide structural evidence for the observed polyQ length threshold in HD pathology. Our approach can be used to validate the effect of pharmacological substances that inhibit or alter amyloid growth and structure.
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Affiliation(s)
- Christoph Röthlein
- Institute of Biochemistry and Biologie and University of Potsdam, 14467 Potsdam.
| | - Markus S Miettinen
- Department of Theory of Biological Soft Matter Systems, Institute of Theoretical Physics, Free University Berlin, 14195 Berlin
| | - Tejas Borwankar
- Institute of Biochemistry and Biologie and University of Potsdam, 14467 Potsdam
| | - Jörg Bürger
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, and
| | - Thorsten Mielke
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Michael U Kumke
- Institute of Chemistry, University of Potsdam, 14467 Potsdam
| | - Zoya Ignatova
- Institute of Biochemistry and Biologie and University of Potsdam, 14467 Potsdam.
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61
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Sahoo B, Singer D, Kodali R, Zuchner T, Wetzel R. Aggregation behavior of chemically synthesized, full-length huntingtin exon1. Biochemistry 2014; 53:3897-907. [PMID: 24921664 PMCID: PMC4075985 DOI: 10.1021/bi500300c] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
![]()
Repeat
length disease thresholds vary among the 10 expanded polyglutamine
(polyQ) repeat diseases, from about 20 to about 50 glutamine residues.
The unique amino acid sequences flanking the polyQ segment are thought
to contribute to these repeat length thresholds. The specific portions
of the flanking sequences that modulate polyQ properties are not always
clear, however. This ambiguity may be important in Huntington’s
disease (HD), for example, where in vitro studies
of aggregation mechanisms have led to distinctly different mechanistic
models. Most in vitro studies of the aggregation
of the huntingtin (HTT) exon1 fragment implicated in the HD mechanism
have been conducted on inexact molecules that are imprecise either
on the N-terminus (recombinantly produced peptides) or on the C-terminus
(chemically synthesized peptides). In this paper, we investigate the
aggregation properties of chemically synthesized HTT exon1 peptides
that are full-length and complete, containing both normal and expanded
polyQ repeat lengths, and compare the results directly to previously
investigated molecules containing truncated C-termini. The results
on the full-length peptides are consistent with a two-step aggregation
mechanism originally developed based on studies of the C-terminally
truncated analogues. Thus, we observe relatively rapid formation of
spherical oligomers containing from 100 to 600 HTT exon1 molecules
and intermediate formation of short protofibril-like structures containing
from 500 to 2600 molecules. In contrast to this relatively rapid assembly,
mature HTT exon1 amyloid requires about one month to dissociate in vitro, which is similar to the time required for neuronal
HTT exon1 aggregates to disappear in vivo after HTT
production is discontinued.
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Affiliation(s)
- Bankanidhi Sahoo
- Department of Structural Biology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States
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62
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Huang RK, Baxa U, Aldrian G, Ahmed AB, Wall JS, Mizuno N, Antzutkin O, Steven AC, Kajava AV. Conformational switching in PolyGln amyloid fibrils resulting from a single amino acid insertion. Biophys J 2014; 106:2134-42. [PMID: 24853742 PMCID: PMC4052364 DOI: 10.1016/j.bpj.2014.03.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 03/18/2014] [Accepted: 03/25/2014] [Indexed: 11/16/2022] Open
Abstract
The established correlation between neurodegenerative disorders and intracerebral deposition of polyglutamine aggregates motivates attempts to better understand their fibrillar structure. We designed polyglutamines with a few lysines inserted to overcome the hindrance of extreme insolubility and two D-lysines to limit the lengths of β-strands. One is 33 amino acids long (PolyQKd-33) and the other has one fewer glutamine (PolyQKd-32). Both form well-dispersed fibrils suitable for analysis by electron microscopy. Electron diffraction confirmed cross-β structures in both fibrils. Remarkably, the deletion of just one glutamine residue from the middle of the peptide leads to substantially different amyloid structures. PolyQKd-32 fibrils are consistently 10-20% wider than PolyQKd-33, as measured by negative staining, cryo-electron microscopy, and scanning transmission electron microscopy. Scanning transmission electron microscopy analysis revealed that the PolyQKd-32 fibrils have 50% higher mass-per-length than PolyQKd-33. This distinction can be explained by a superpleated β-structure model for PolyQKd-33 and a model with two β-solenoid protofibrils for PolyQKd-32. These data provide evidence for β-arch-containing structures in polyglutamine fibrils and open future possibilities for structure-based drug design.
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Affiliation(s)
- Rick K Huang
- Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland
| | - Ulrich Baxa
- Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland; Electron Microscopy Laboratory, Cancer Research Technology Program, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, Maryland
| | - Gudrun Aldrian
- Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier 1 and 2, Montpellier, France
| | - Abdullah B Ahmed
- Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier 1 and 2, Montpellier, France
| | - Joseph S Wall
- Department of Biology, Brookhaven National Laboratory, Upton New York
| | - Naoko Mizuno
- Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland; Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, Martinsried, Germany
| | - Oleg Antzutkin
- Chemistry of Interfaces, Luleå University of Technology, Luleå, Sweden; Department of Physics, Warwick University, Coventry, United Kingdom
| | - Alasdair C Steven
- Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland.
| | - Andrey V Kajava
- Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier 1 and 2, Montpellier, France; Institut de Biologie Computationnelle, Montpellier, France; University ITMO, 197101 St. Petersburg, Russia.
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63
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Hoffner G, Djian P. Monomeric, oligomeric and polymeric proteins in huntington disease and other diseases of polyglutamine expansion. Brain Sci 2014; 4:91-122. [PMID: 24961702 PMCID: PMC4066239 DOI: 10.3390/brainsci4010091] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 02/06/2014] [Accepted: 02/18/2014] [Indexed: 01/03/2023] Open
Abstract
Huntington disease and other diseases of polyglutamine expansion are each caused by a different protein bearing an excessively long polyglutamine sequence and are associated with neuronal death. Although these diseases affect largely different brain regions, they all share a number of characteristics, and, therefore, are likely to possess a common mechanism. In all of the diseases, the causative protein is proteolyzed, becomes abnormally folded and accumulates in oligomers and larger aggregates. The aggregated and possibly the monomeric expanded polyglutamine are likely to play a critical role in the pathogenesis and there is increasing evidence that the secondary structure of the protein influences its toxicity. We describe here, with special attention to huntingtin, the mechanisms of polyglutamine aggregation and the modulation of aggregation by the sequences flanking the polyglutamine. We give a comprehensive picture of the characteristics of monomeric and aggregated polyglutamine, including morphology, composition, seeding ability, secondary structure, and toxicity. The structural heterogeneity of aggregated polyglutamine may explain why polyglutamine-containing aggregates could paradoxically be either toxic or neuroprotective.
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Affiliation(s)
- Guylaine Hoffner
- Génétique moléculaire et défense antivirale, Centre National de la Recherche Scientifique, Université Paris Descartes, 45 rue des Saints Pères, 75006 Paris, France.
| | - Philippe Djian
- Génétique moléculaire et défense antivirale, Centre National de la Recherche Scientifique, Université Paris Descartes, 45 rue des Saints Pères, 75006 Paris, France.
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64
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Abstract
A significant body of evidence shows that polyglutamine (polyQ) tracts are important for various biological functions. The characteristic polymorphism of polyQ length is thought to play an important role in the adaptation of organisms to their environment. However, proteins with expanded polyQ are prone to form amyloids, which cause diseases in humans and animals and toxicity in yeast. Saccharomyces cerevisiae contain at least 8 proteins which can form heritable amyloids, called prions, and most of them are proteins with glutamine- and asparagine-enriched domains. Yeast prion amyloids are susceptible to fragmentation by the protein disaggregase Hsp104, which allows them to propagate and be transmitted to daughter cells during cell divisions. We have previously shown that interspersion of polyQ domains with some non-glutamine residues stimulates fragmentation of polyQ amyloids in yeast and that yeast prion domains are often enriched in one of these residues. These findings indicate that yeast prion domains may have derived from polyQ tracts via accumulation and amplification of mutations. The same hypothesis may be applied to polyasparagine (polyN) tracts, since they display similar properties to polyQ, such as length polymorphism, amyloid formation and toxicity. We propose that mutations in polyQ/N may be favored by natural selection thus making prion domains likely by-products of the evolution of polyQ/N.
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65
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Unmasking the roles of N- and C-terminal flanking sequences from exon 1 of huntingtin as modulators of polyglutamine aggregation. Proc Natl Acad Sci U S A 2013; 110:20075-80. [PMID: 24282292 DOI: 10.1073/pnas.1320626110] [Citation(s) in RCA: 160] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Huntington disease is caused by mutational expansion of the CAG trinucleotide within exon 1 of the huntingtin (Htt) gene. Exon 1 spanning N-terminal fragments (NTFs) of the Htt protein result from aberrant splicing of transcripts of mutant Htt. NTFs typically encompass a polyglutamine tract flanked by an N-terminal 17-residue amphipathic stretch (N17) and a C-terminal 38-residue proline-rich stretch (C38). We present results from in vitro biophysical studies that quantify the driving forces for and mechanisms of polyglutamine aggregation as modulated by N17 and C38. Although N17 is highly soluble by itself, it lowers the saturation concentration of soluble NTFs and increases the driving force, vis-à-vis homopolymeric polyglutamine, for forming insoluble aggregates. Kinetically, N17 accelerates fibril formation and destabilizes nonfibrillar intermediates. C38 is also highly soluble by itself, and it lends its high intrinsic solubility to lower the driving force for forming insoluble aggregates by increasing the saturation concentration of soluble NTFs. In NTFs with both modules, N17 and C38 act synergistically to destabilize nonfibrillar intermediates (N17 effect) and lower the driving force for forming insoluble aggregates (C38 effect). Morphological studies show that N17 and C38 promote the formation of ordered fibrils by NTFs. Homopolymeric polyglutamine forms a mixture of amorphous aggregates and fibrils, and its aggregation mechanisms involve early formation of heterogeneous distributions of nonfibrillar species. We propose that N17 and C38 act as gatekeepers that control the intrinsic heterogeneities of polyglutamine aggregation. This provides a biophysical explanation for the modulation of in vivo NTF toxicities by N17 and C38.
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66
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Stefl S, Nishi H, Petukh M, Panchenko AR, Alexov E. Molecular mechanisms of disease-causing missense mutations. J Mol Biol 2013; 425:3919-36. [PMID: 23871686 DOI: 10.1016/j.jmb.2013.07.014] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 07/04/2013] [Accepted: 07/10/2013] [Indexed: 12/23/2022]
Abstract
Genetic variations resulting in a change of amino acid sequence can have a dramatic effect on stability, hydrogen bond network, conformational dynamics, activity and many other physiologically important properties of proteins. The substitutions of only one residue in a protein sequence, so-called missense mutations, can be related to many pathological conditions and may influence susceptibility to disease and drug treatment. The plausible effects of missense mutations range from affecting the macromolecular stability to perturbing macromolecular interactions and cellular localization. Here we review the individual cases and genome-wide studies that illustrate the association between missense mutations and diseases. In addition, we emphasize that the molecular mechanisms of effects of mutations should be revealed in order to understand the disease origin. Finally, we report the current state-of-the-art methodologies that predict the effects of mutations on protein stability, the hydrogen bond network, pH dependence, conformational dynamics and protein function.
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Affiliation(s)
- Shannon Stefl
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson, SC 29634, USA
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67
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Shenberger Y, Yarmiayev V, Ruthstein S. Exploring the interaction between the human copper transporter, CTR1, c-terminal domain and a methionine motif in the presence of Cu(I) and Ag(I) ions, using EPR spectroscopy. Mol Phys 2013. [DOI: 10.1080/00268976.2013.807947] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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68
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Kar K, Hoop CL, Drombosky KW, Baker MA, Kodali R, Arduini I, van der Wel PCA, Horne WS, Wetzel R. β-hairpin-mediated nucleation of polyglutamine amyloid formation. J Mol Biol 2013; 425:1183-97. [PMID: 23353826 PMCID: PMC3602386 DOI: 10.1016/j.jmb.2013.01.016] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 01/15/2013] [Accepted: 01/15/2013] [Indexed: 12/01/2022]
Abstract
The conformational preferences of polyglutamine (polyQ) sequences are of major interest because of their central importance in the expanded CAG repeat diseases that include Huntington's disease. Here, we explore the response of various biophysical parameters to the introduction of β-hairpin motifs within polyQ sequences. These motifs (tryptophan zipper, disulfide, d-Pro-Gly, Coulombic attraction, l-Pro-Gly) enhance formation rates and stabilities of amyloid fibrils with degrees of effectiveness well correlated with their known abilities to enhance β-hairpin formation in other peptides. These changes led to decreases in the critical nucleus for amyloid formation from a value of n=4 for a simple, unbroken Q23 sequence to approximate unitary n values for similar length polyQs containing β-hairpin motifs. At the same time, the morphologies, secondary structures, and bioactivities of the resulting fibrils were essentially unchanged from simple polyQ aggregates. In particular, the signature pattern of solid-state NMR (13)C Gln resonances that appears to be unique to polyQ amyloid is replicated exactly in fibrils from a β-hairpin polyQ. Importantly, while β-hairpin motifs do produce enhancements in the equilibrium constant for nucleation in aggregation reactions, these Kn values remain quite low (~10(-)(10)) and there is no evidence for significant enhancement of β-structure within the monomer ensemble. The results indicate an important role for β-turns in the nucleation mechanism and structure of polyQ amyloid and have implications for the nature of the toxic species in expanded CAG repeat diseases.
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Affiliation(s)
- Karunakar Kar
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA
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69
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Burke KA, Kauffman KJ, Umbaugh CS, Frey SL, Legleiter J. The interaction of polyglutamine peptides with lipid membranes is regulated by flanking sequences associated with huntingtin. J Biol Chem 2013; 288:14993-5005. [PMID: 23572526 DOI: 10.1074/jbc.m112.446237] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Huntington disease (HD) is caused by an expanded polyglutamine (poly(Q)) repeat near the N terminus of the huntingtin (htt) protein. Expanded poly(Q) facilitates formation of htt aggregates, eventually leading to deposition of cytoplasmic and intranuclear inclusion bodies containing htt. Flanking sequences directly adjacent to the poly(Q) domain, such as the first 17 amino acids on the N terminus (Nt17) and the polyproline (poly(P)) domain on the C-terminal side of the poly(Q) domain, heavily influence aggregation. Additionally, htt interacts with a variety of membraneous structures within the cell, and Nt17 is implicated in lipid binding. To investigate the interaction between htt exon1 and lipid membranes, a combination of in situ atomic force microscopy, Langmuir trough techniques, and vesicle permeability assays were used to directly monitor the interaction of a variety of synthetic poly(Q) peptides with different combinations of flanking sequences (KK-Q35-KK, KK-Q35-P10-KK, Nt17-Q35-KK, and Nt17-Q35-P10-KK) on model membranes and surfaces. Each peptide aggregated on mica, predominately forming extended, fibrillar aggregates. In contrast, poly(Q) peptides that lacked the Nt17 domain did not appreciably aggregate on or insert into lipid membranes. Nt17 facilitated the interaction of peptides with lipid surfaces, whereas the poly(P) region enhanced this interaction. The aggregation of Nt17-Q35-P10-KK on the lipid bilayer closely resembled that of a htt exon1 construct containing 35 repeat glutamines. Collectively, this data suggests that the Nt17 domain plays a critical role in htt binding and aggregation on lipid membranes, and this lipid/htt interaction can be further modulated by the presence of the poly(P) domain.
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Affiliation(s)
- Kathleen A Burke
- C Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26505, USA
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70
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Mishra R, Hoop CL, Kodali R, Sahoo B, van der Wel PCA, Wetzel R. Serine phosphorylation suppresses huntingtin amyloid accumulation by altering protein aggregation properties. J Mol Biol 2012; 424:1-14. [PMID: 22999956 DOI: 10.1016/j.jmb.2012.09.011] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 09/01/2012] [Accepted: 09/10/2012] [Indexed: 11/17/2022]
Abstract
Aggregation of expanded polyglutamine repeat-containing fragments of the huntingtin (htt) protein may play a key role in Huntington's disease. Consistent with this hypothesis, two Ser-to-Asp mutations in the 17-amino-acid N-terminal htt(NT) segment abrogate both visible brain aggregates and disease symptoms in a full-length Q(97) htt mouse model while compromising aggregation kinetics and aggregate morphology in an htt fragment in vitro [Gu et al. (2009). Serines 13 and 16 are critical determinants of full-length human mutant huntingtin induced disease pathogenesis in HD mice. Neuron64, 828-840]. The htt(NT) segment has been shown to play a critical role in facilitating nucleation of amyloid formation in htt N-terminal exon1 fragments. We show here how these Ser-to-Asp mutations dramatically affect aggregation kinetics and aggregate structural integrity. First, these negatively charged Ser replacements impair the assembly of the α-helical oligomers that play a critical role in htt amyloid nucleation, thus providing an explanation for reduced amyloid formation rates. Second, these sequence modifications alter aggregate morphology, decrease aggregate stability, and enhance the steric accessibility of the htt(NT) segment within the aggregates. Together, these changes make the sequence-modified peptides kinetically and thermodynamically less likely to aggregate and more susceptible, if they do, to posttranslational modifications and degradation. These effects also show how phosphorylation of a protein might achieve cellular effects via direct impacts on the protein's aggregation properties. In fact, preliminary studies on exon1-like molecules containing phosphoryl-Ser residues at positions 13 and 16 show that they reduce aggregation rates and generate atypical aggregate morphologies similar to the effects of the Ser-to-Asp mutants.
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Affiliation(s)
- Rakesh Mishra
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA.
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