scholarly journals Amyloid fibrils prepared using an acetylated and methyl amidated peptide model of the α-Synuclein NAC 71–82 amino acid stretch contain an additional cross-β structure also found in prion proteins

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Thomas Näsström ◽  
Per Ola Andersson ◽  
Christian Lejon ◽  
Björn C. G. Karlsson
Keyword(s):  
Amino Acid ◽  
Protein Misfolding ◽  
Prion Proteins ◽  
Lewy Bodies ◽  
Amyloid Β ◽  
Full Length ◽  
Aggregation Propensity ◽  
Amino Acid Stretch ◽  
Amidated Peptide ◽  
Β Sheet

Abstract The 71–82 fragment of the non-amyloid-β component (NAC) region of the Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) related protein α-Synuclein, has been reported to be important during protein misfolding. Although reports have demonstrated the importance of this fragment for the aggregation properties of the full-length protein, its exact role in pre-fibrillar oligomerisation, fibrillar growth and morphology has not yet been fully elucidated. Here, we provide evidence that fibrils prepared from an acetylated and methyl amidated peptide of the NAC 71–82 amino acid stretch of α-Synuclein are amyloid and contain, in addition to the cross-β structure detected in the full-length protein fibrils, a cross-β structure previously observed in prion proteins. These results shed light on the aggregation propensity of the NAC 71–82 amino acid stretch of the full-length protein but also the roles of the N- and C-terminal domains of α-Synuclein in balancing this aggregation propensity. The results also suggest that early aggregated forms of the capped NAC 71–82 peptide generated structures were stabilised by an anti-parallel and twisted β-sheet motif. Due to its expected toxicity, this β-sheet motif may be a promising molecular target for the development of therapeutic strategies for PD and DLB.

scholarly journals A Capped Peptide of the Aggregation Prone NAC 71–82 Amino Acid Stretch of α-Synuclein Folds into Soluble β-Sheet Oligomers at Low and Elevated Peptide Concentrations

2020 ◽  
Vol 21 (5) ◽  
pp. 1629 ◽  
Author(s):  
Thomas Näsström ◽  
Jörgen Ådén ◽  
Fumina Shibata ◽  
Per Ola Andersson ◽  
Björn C.G. Karlsson
Keyword(s):  
Amino Acid ◽  
Prion Proteins ◽  
Lewy Bodies ◽  
Amyloid Β ◽  
Aggregation Kinetics ◽  
Lewy Neurites ◽  
Aggregation Propensity ◽  
Amino Acid Stretch ◽  
Dynamics Simulations ◽  
Β Sheet

Although Lewy bodies and Lewy neurites are hallmarks of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB), misfolded α-synuclein oligomers are nowadays believed to be key for the development of these diseases. Attempts to target soluble misfolded species of the full-length protein have been limited so far, probably due to the fast aggregation kinetics and burial of aggregation prone segments in final cross-β-sheet fibrils. A previous characterisation study of fibrils prepared from a capped peptide of the non-amyloid β-component (NAC) 71–82 amino acid stretch of α-synuclein demonstrated an increased aggregation propensity resulting in a cross-β-structure that is also found in prion proteins. From this, it was suggested that capped NAC 71–82 peptide oligomers would provide interesting motifs with a capacity to regulate disease development. Here, we demonstrated, from a series of circular dichroism spectroscopic measurements and molecular dynamics simulations, the molecular-environment-sensitive behaviour of the capped NAC 71–82 peptide in a solution phase and the formation of β-sheet oligomeric structures in the supernatant of a fibrillisation mixture. These results highlighted the use of the capped NAC 71–82 peptide as a motif in the preparation of oligomeric β-sheet structures that potentially could be used in therapeutic strategies in the fight against progressive neurodegenerative disorders, such as PD and DLB.

Studies of the aggregation of an amyloidogenic α-synuclein peptide fragment

2005 ◽  
Vol 33 (5) ◽  
pp. 1113-1115 ◽  
Author(s):  
J. Madine ◽  
A.J. Doig ◽  
A. Kitmitto ◽  
D.A. Middleton
Keyword(s):  
Structural Analysis ◽  
Characteristic Feature ◽  
Neurodegenerative Disorders ◽  
Lewy Bodies ◽  
Structural Features ◽  
Full Length ◽  
Peptide Fragment ◽  
Structural Investigations ◽  
Detailed Structural Analysis ◽  
Β Sheet

The deposition of α-syn (α-synuclein) fibrils in Lewy bodies is a characteristic feature of individuals with neurodegenerative disorders. A peptide comprising the central residues 71–82 of α-syn [α-syn(71–82)] is capable of forming β-sheet-rich, amyloid-like fibrils with similar morphologies to fibrils of the full-length protein, providing a useful model of pathogenic α-syn fibrils that is suitable for detailed structural analysis. We have studied the morphology and gross structural features of α-syn(71–82) fibrils formed under different conditions in order to obtain reliable conditions for producing fibrils for further structural investigations. The results indicate that the rate of aggregation and the morphology of the fibrils formed are sensitive to pH and temperature.

scholarly journals Exceptional aggregation propensity of amino acids in polyglutamine amino-acid-homopolymer

2020 ◽  
Author(s):  
Rahul Mishra ◽  
Ashwani K. Thakur
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Van Der Waals ◽  
Physicochemical Characteristic ◽  
Aggregation Behavior ◽  
Human Proteome ◽  
Van Der Waals Volume ◽  
Aggregation Propensity ◽  
Starting Point ◽  
Β Sheet

AbstractSimilar aggregation and β-sheet propensity of amino acids in globular proteins and amyloids, suggests comparable principles of their formation. Here we show that during the process of aggregation into amyloid-like fibers, these rules are not the same in an amino-acid-homopolymer (AAHP) polyglutamine (PolyGln). An aggregation kinetic analysis on nine-point mutants of a forty-six long PolyGln peptide was carried in physiological conditions. At the dynamic equilibrium state of aggregation, critical-concentration derived free-energy differences, signifying aggregation propensity of incorporated amino acids were obtained. None of the obtained propensities correlated with existing conventional aggregation and β-sheet propensities of the amino acids in proteins and amyloids. Further, the differential aggregation behavior of all the peptides only correlated with van der Waals volume of the incorporated amino acid and not with any other physicochemical characteristic of amino acids. The new rules obtained from PolyGln AAHP provide an opportunity to explore physiological relevance of a mutation within AAHP in human proteome. Additionally, this study opens up new avenues for protein model design exploring folding and aggregation behavior of other amino-acid-homopolymer (AAHP) existing in the human proteome.SignificanceMutational analysis within PolyGln sequences adds to the knowledge of unique aggregation propensities of amino acids within PolyGln AAHP. This study highlights the importance of van der Waals volume in dictating stability-instability of an aggregation fold and in turn aggregation kinetics and thermodynamic stability of aggregates. The analysis signifies the role of Gln-Gln interlocking system within PolyGln folding motif and extent of disruption caused by van der Waals volume of an amino acid. The results can be taken as a starting point to evaluate the possible impact of amino acid insertions in PolyGln stretches of other proteins. It also opens opportunities to study the structural and functional relationship of other AAHPS for their unique folding and aggregation behavior. Learning outcome can be utilized as a bottom–up approach to design amyloid biomaterial with different strengths for biomedical applications.

Using Small Peptide Segments of Amyloid-β and Humanin to Examine their Physical Interactions

2019 ◽  
Vol 26 (7) ◽  
pp. 502-511 ◽  
Author(s):  
Deborah L. Heyl ◽  
Brandon Iwaniec ◽  
Daniel Esckilsen ◽  
Deanna Price ◽  
Prathyusha Guttikonda ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Full Length ◽  
Binding Kinetics ◽  
Amino Acid Residues ◽  
Aβ Peptides ◽  
Physical Interactions ◽  
Peptide Segments ◽  
Kinetics Of

Background: Amyloid fibrils in Alzheimer’s disease are composed of amyloid-β (Aβ) peptides of variant lengths. Humanin (HN), a 24 amino acid residue neuroprotective peptide, is known to interact with the predominant Aβ isoform in the brain, Aβ (1-40). Methods: Here, we constructed smaller segments of Aβ and HN and identified residues in HN important for both HN-HN and HN-Aβ interactions. Peptides corresponding to amino acid residues 5- 15 of HN, HN (5-15), HN (5-15, L11S), where Leu11 was replaced with Ser, and residues 17-28 of Aβ, Aβ (17-28), were synthesized and tested for their ability to block formation of the complex between HN and Aβ (1-40). Results: Co-immunoprecipitation and binding kinetics showed that HN (5-15) was more efficient at blocking the complex between HN and Aβ (1-40) than either HN (5-15, L11S) or Aβ (17-28). Binding kinetics of these smaller peptides with either full-length HN or Aβ (1-40) showed that HN (5- 15) was able to bind either Aβ (1-40) or HN more efficiently than HN (5-15, L11S) or Aβ (17-28). Compared to full-length HN, however, HN (5-15) bound Aβ (1-40) with a weaker affinity suggesting that while HN (5-15) binds Aβ, other residues in the full length HN peptide are necessary for maximum interactions. Conclusion: L11 was more important for interactions with Aβ (1-40) than with HN. Aβ (17-28) was relatively ineffective at binding to either Aβ (1-40) or HN. Moreover, HN, and the smaller HN (5-15), HN (5-15 L11S), and Aβ (17-28) peptides, had different effects on regulating Aβ (1-40) aggregation kinetics.

The p3 Peptide, a Naturally Occurring Fragment of the Amyloid-β Peptide (Aβ)Found in Alzheimer's Disease, Has a Greater Aggregation Propensity In Vitro Than Full-Length Aβ, But Does Not Bind Cu2+.

2000 ◽  
Vol 53 (4) ◽  
pp. 321 ◽  
Author(s):  
Feda Ali ◽  
Andrew J. Thompson ◽  
Colin J. Barrow
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Down's Syndrome ◽  
Amyloid Β ◽  
Down’S Syndrome ◽  
Full Length ◽  
Amyloid Β Peptide ◽  
Sheet Structure ◽  
Β Sheet

Cerebellar preamyloid from both Down’s syndrome and Alzheimer’s disease contains the p3 fragment (Aβ 17–40/42) as a major amyloid-β peptide (Aβ) component. The p3 peptide was previously shown to form amyloid in vitro, but less readily than full-length Aβ. Here we show that the p3 peptide has a greater β-sheet-forming propensity than full-length Aβ. Using circular dichroism spectroscopy we determined that in aqueous solutions the p3 peptide forms β-sheet structure more readily than full-length Aβ. The p3 peptide also has a lower α-helical propensity than full-length Aβ in the structure-forming solvent trifluoroethanol. These results indicate that the lower amyloidogenicity of the p3 peptide is not related to an inability to form β-sheet structure. In this study we also show that, unlike full-length Aβ, the p3 peptide does not bind Cu2+ ions. This inability to bind copper ions may explain why the p3 peptide appears to play a lesser role in Down’s syndrome and Alzheimer’s disease related neurodegeneration than does full-length Aβ.

scholarly journals Tandem-Homodimer of a β-Sheet-Forming Short Peptide Inhibits Random-to-β Structural Transition of Its Original Monomer

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1421
Author(s):  
Kin-ya Tomizaki ◽  
Tomomi Iori ◽  
Hideyasu Fukushima ◽  
Yasuhiro Nakabayashi ◽  
Yoshiki Matsumoto ◽  
...  
Keyword(s):  
Amino Acid ◽  
Structural Transition ◽  
Amyloid Β ◽  
Sheet Forming ◽  
Aβ Peptide ◽  
Short Peptide ◽  
New Class ◽  
In Series ◽  
Chain Lengths ◽  
Β Sheet

There is an increasing interest in designing fibrillogenesis modulators for treating amyloid β (Aβ)-peptide-associated diseases. The use of Aβ fragment peptides and their derivatives, as well as nonpeptidyl natural products, is one promising approach to prevent Aβ fibrillation. In this study, we demonstrate that tandem-homodimers (TDs) of a β-sheet-forming short peptide in which the amino acid sequence is duplicated in series and joined via an amino alkanoic acid linker of different chain lengths, preventing the random-to-β structural transition of the original monomer. Ape5-TD, containing 5-amino pentanoate, most potently prevented this transition for at least five days by generating disordered aggregates with reduced tryptic stability. The linkers in the TDs generated this inhibitory activity, probably due to their bent conformations and hydrophobicity, appropriate for accommodating and twisting the monomers, resulting in irregular arrangements of the peptides. The present study could allow the design of a new class of protein/peptide fibrillogenesis modulators.

scholarly journals Anti-Parallel β-Hairpin Structure in Soluble Aβ Oligomers of Aβ40-Dutch and Aβ40-Iowa

2021 ◽  
Vol 22 (3) ◽  
pp. 1225
Author(s):  
Ziao Fu ◽  
William E. Van Nostrand ◽  
Steven O. Smith
Keyword(s):  
Amyloid Β ◽  
Amyloid Angiopathy ◽  
Aβ Oligomers ◽  
Dominant Component ◽  
Fibril Structure ◽  
Predominant Component ◽  
Aβ Aggregation ◽  
Aβ Fibrils ◽  
Soluble Aβ Oligomers ◽  
Β Sheet

The amyloid-β (Aβ) peptides are associated with two prominent diseases in the brain, Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA). Aβ42 is the dominant component of cored parenchymal plaques associated with AD, while Aβ40 is the predominant component of vascular amyloid associated with CAA. There are familial CAA mutations at positions Glu22 and Asp23 that lead to aggressive Aβ aggregation, drive vascular amyloid deposition and result in degradation of vascular membranes. In this study, we compared the transition of the monomeric Aβ40-WT peptide into soluble oligomers and fibrils with the corresponding transitions of the Aβ40-Dutch (E22Q), Aβ40-Iowa (D23N) and Aβ40-Dutch, Iowa (E22Q, D23N) mutants. FTIR measurements show that in a fashion similar to Aβ40-WT, the familial CAA mutants form transient intermediates with anti-parallel β-structure. This structure appears before the formation of cross-β-sheet fibrils as determined by thioflavin T fluorescence and circular dichroism spectroscopy and occurs when AFM images reveal the presence of soluble oligomers and protofibrils. Although the anti-parallel β-hairpin is a common intermediate on the pathway to Aβ fibrils for the four peptides studied, the rate of conversion to cross-β-sheet fibril structure differs for each.

scholarly journals Assessment of Amyloid Forming Tendency of Peptide Sequences from Amyloid Beta and Tau Proteins Using Force-Field, Semi-Empirical, and Density Functional Theory Calculations

2021 ◽  
Vol 22 (6) ◽  
pp. 3244
Author(s):  
Charuvaka Muvva ◽  
Natarajan Arul Murugan ◽  
Venkatesan Subramanian
Keyword(s):  
Force Field ◽  
Density Functional ◽  
Amyloid Β ◽  
Density Functional Theory Calculations ◽  
Tau Proteins ◽  
Functional Theory ◽  
Energy Profiles ◽  
Α Helix ◽  
Semi Empirical ◽  
Β Sheet

A wide variety of neurodegenerative diseases are characterized by the accumulation of protein aggregates in intraneuronal or extraneuronal brain regions. In Alzheimer’s disease (AD), the extracellular aggregates originate from amyloid-β proteins, while the intracellular aggregates are formed from microtubule-binding tau proteins. The amyloid forming peptide sequences in the amyloid-β peptides and tau proteins are responsible for aggregate formation. Experimental studies have until the date reported many of such amyloid forming peptide sequences in different proteins, however, there is still limited molecular level understanding about their tendency to form aggregates. In this study, we employed umbrella sampling simulations and subsequent electronic structure theory calculations in order to estimate the energy profiles for interconversion of the helix to β-sheet like secondary structures of sequences from amyloid-β protein (KLVFFA) and tau protein (QVEVKSEKLD and VQIVYKPVD). The study also included a poly-alanine sequence as a reference system. The calculated force-field based free energy profiles predicted a flat minimum for monomers of sequences from amyloid and tau proteins corresponding to an α-helix like secondary structure. For the parallel and anti-parallel dimer of KLVFFA, double well potentials were obtained with the minima corresponding to α-helix and β-sheet like secondary structures. A similar double well-like potential has been found for dimeric forms for the sequences from tau fibril. Complementary semi-empirical and density functional theory calculations displayed similar trends, validating the force-field based free energy profiles obtained for these systems.

scholarly journals Multiple system atrophy-associated oligodendroglial protein p25α stimulates formation of novel α-synuclein strain with enhanced neurodegenerative potential

2021 ◽  
Author(s):  
Nelson Ferreira ◽  
Hjalte Gram ◽  
Zachary A. Sorrentino ◽  
Emil Gregersen ◽  
Sissel Ida Schmidt ◽  
...  
Keyword(s):  
Multiple System Atrophy ◽  
Protein Misfolding ◽  
Resonance Energy Transfer ◽  
Lewy Bodies ◽  
Resonance Energy ◽  
Alpha Synuclein ◽  
Striatal Neurons ◽  
End Stage ◽  
Intracellular Aggregates

AbstractPathology consisting of intracellular aggregates of alpha-Synuclein (α-Syn) spread through the nervous system in a variety of neurodegenerative disorders including Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy. The discovery of structurally distinct α-Syn polymorphs, so-called strains, supports a hypothesis where strain-specific structures are templated into aggregates formed by native α-Syn. These distinct strains are hypothesised to dictate the spreading of pathology in the tissue and the cellular impact of the aggregates, thereby contributing to the variety of clinical phenotypes. Here, we present evidence of a novel α-Syn strain induced by the multiple system atrophy-associated oligodendroglial protein p25α. Using an array of biophysical, biochemical, cellular, and in vivo analyses, we demonstrate that compared to α-Syn alone, a substoichiometric concentration of p25α redirects α-Syn aggregation into a unique α-Syn/p25α strain with a different structure and enhanced in vivo prodegenerative properties. The α-Syn/p25α strain induced larger inclusions in human dopaminergic neurons. In vivo, intramuscular injection of preformed fibrils (PFF) of the α-Syn/p25α strain compared to α-Syn PFF resulted in a shortened life span and a distinct anatomical distribution of inclusion pathology in the brain of a human A53T transgenic (line M83) mouse. Investigation of α-Syn aggregates in brain stem extracts of end-stage mice demonstrated that the more aggressive phenotype of the α-Syn/p25α strain was associated with an increased load of α-Syn aggregates based on a Förster resonance energy transfer immunoassay and a reduced α-Syn aggregate seeding activity based on a protein misfolding cyclic amplification assay. When injected unilaterally into the striata of wild-type mice, the α-Syn/p25α strain resulted in a more-pronounced motoric phenotype than α-Syn PFF and exhibited a “tropism” for nigro-striatal neurons compared to α-Syn PFF. Overall, our data support a hypothesis whereby oligodendroglial p25α is responsible for generating a highly prodegenerative α-Syn strain in multiple system atrophy.

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