A New Amyloid-Like β-Aggregate with Amyloid Characteristics, Except Fibril Morphology

Chang, Evan S.-H.; Liao, Tai-Yan; Lim, Tsong–Shin; Fann, Wunshain; Chen, Rita P.‐Y.

doi:10.1016/j.jmb.2008.11.009

Cited by 24 publications

(23 citation statements)

References 48 publications

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“…Notably, Val 24 is the most hydrophobic amino acid replaced in this analysis. Chen et al have reported a C r of 29.44 µM for this peptide; 44 the difference in C r between Chen’s report and our work is most likely due to differences in solvent composition. Our fibril samples contain a final DMSO concentration of 5%, which has a destabilizing effect on fibril stability.…”

Section: Resultscontrasting

confidence: 84%

“…48 It should be noted that centrifugation may not be able to separate fibril and higher order oligmer species from lower-order non-fibrillar aggregates (dimer, trimer, etc.). Further, amorphous aggregates may represent a common intermediate during the complex folding pathway of Aβ variants; 44 these aggregates would be indistinguishable from cross-β fibrils during centrifugation. Nevertheless, this sedimentation HPLC assay has become a standard technique to approximate fibril stability.…”

Section: Resultsmentioning

confidence: 99%

“…Recent work by Chen et al shows that turn nucleation by D PG incorporation at position 24/25 destabilizes the resulting aggregates thermodynamically; these results indicate that β-hairpin nucleation of the monomeric peptide perturbs the selfassembly pathway. 44 Given this recent evidence that a β-hairpin intermediate may exist during fibrillogenesis, the role of β-hairpin formation on Aβ fibril self-assembly has not been thoroughly addressed in terms of position of turn nucleation. The possible role of turn nucleation in the formation of cytotoxic prefibrillar oligomers has also not been thoroughly characterized.…”

Section: Discussionmentioning

confidence: 99%

“…have previously shown that D PG at positions 24–25 (Val 24 → D Pro Aβ40) results in thermodynamic destabilization of the resulting fibril aggregates relative to the wild-type peptide. 44 The studies reported herein complement Chen’s work by kinetically and thermodynamically characterizing the positional effect of D PG turn nucleation throughout the putative turn region in order to gain insight into 1) a possible role for β-hairpin formation early in Aβ self-assembly processes, 2) how the position of turn nucleation relative to formation of the D23/K28 salt bridge influences Aβ self-assembly, and 3) how turn nucleation correlates to cytotoxicity of the resulting aggregate species. We found that including a turn motif between residues 24 and 27 of Aβ40 generally enhanced the rate of selfassembly relative to wild-type, with the D PG-25,26 and D PG-26,27 variants forming fibrils without an apparent lag phase; the D PG-24,25 variant forms fibrils at a moderately faster rate than wild-type.…”

Section: Introductionmentioning

confidence: 99%

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Turn Nucleation Perturbs Amyloid β Self-Assembly and Cytotoxicity

Doran

Anderson

Latchney

et al. 2012

Journal of Molecular Biology

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The accumulation of senile plaques composed of amyloid-β (Aβ) fibrils is a hallmark of Alzheimer’s disease (AD), although prefibrillar oligomeric species are believed to be the primary neurotoxic congeners in AD pathogenesis. Uncertainty regarding the mechanistic relationship between Aβ oligomer and fibril formation and the cytotoxicity of these aggregate species persists. β-Turn formation has been proposed to be a potential rate limiting step during Aβ fibrillogenesis. The effect of turn nucleation on Aβ self-assembly was probed by systematically replacing amino acid pairs in the putative turn region of Aβ (residues 24–27) with d-ProGly, an effective turn nucleating motif. The kinetic, thermodynamic, and cytotoxic effects of these mutations were characterized. It was found that turn formation dramatically accelerated Aβ fibril self-assembly dependent on the site of turn nucleation. The cytotoxicity of the three d-ProGlycontaining Aβ variants was significantly lower than that of wild-type Aβ40, presumably due to decreased oligomer populations as a function of more rapid progression to mature fibrils; oligomer populations were not eliminated, however, suggesting that turn formation is also a feature of oligomer structures. These results indicate that turn nucleation is a critical step in Aβ40 fibril formation.

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Section: Resultscontrasting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Turn Nucleation Perturbs Amyloid β Self-Assembly and Cytotoxicity

Doran

Anderson

Latchney

et al. 2012

Journal of Molecular Biology

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“…An important tool used to probe transition-state structure in protein folding is the so-called φ-value or protein engineering method. However, this methodology is much less likely to be useful for studies of amyloid formation because the pathway of amyloid formation can be perturbed by mutations, amyloid fibrils can be polymorphic, and fibril morphology can be altered by seemingly modest changes in primary sequence or in solution conditions 9–12. CD spectroscopy probes secondary-structure formation but is not residue-specific.…”

Section: Introductionmentioning

confidence: 99%

Residue-Specific, Real-Time Characterization of Lag-Phase Species and Fibril Growth During Amyloid Formation: A Combined Fluorescence and IR Study of p-Cyanophenylalanine Analogs of Islet Amyloid Polypeptide

Marek

Mukherjee

Zanni

et al. 2010

Journal of Molecular Biology

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Amyloid formation normally exhibits a lag phase followed by a growth phase, which leads to amyloid fibrils. Characterization of the species populated during the lag phase is experimentally challenging, but is critical since the most toxic entities may be pre-fibrillar species. p-Cyanophenylalanine (FC≡N) fluorescence is used to probe the nature of lag-phase species populated during the formation of amyloid by human islet amyloid polypeptide. The polypeptide contains two phenylalanines at positions 15 and 23 and a single tyrosine located at the C-terminus. Each aromatic residue was separately replaced by FC≡N. The substitutions do not perturb amyloid formation relative to wild-type islet amyloid polypeptide as detected using thioflavin T fluorescence and electron microscopy. FC≡N fluorescence is high when the cyano group is hydrogen bonded and low when it is not. It can also be quenched via Förster resonance energy transfer to tyrosine. Fluorescence intensity was monitored in real time and revealed that all three positions remained exposed to solvent during the lag phase but less exposed than unstructured model peptides. The time course of amyloid formation as monitored by thioflavin T fluorescence and FC≡N fluorescence is virtually identical. Fluorescence quenching experiments confirmed that each residue remains exposed during the lag phase. These results place significant constraints on the nature of intermediates that are populated during the lag phase and indicate that significant sequestering of the aromatic side chains does not occur until β-structure sufficient to bind thioflavin T has developed. Seeding studies and analysis of maximum rates confirm that sequestering of the cyano groups occurs concomitantly with the development of thioflavin T binding capability. Overall, the process of amyloid formation and growth appears to be remarkably homogenous in terms of side-chain ordering. FC≡N also provides information about fibril structure. Fluorescence emission measurements, infrared measurements, and quenching studies indicate that the aromatic residues are differentially exposed in the fibril state with Phe15 being the most exposed. FC≡N is readily accommodated into proteins; thus, the approach should be broadly applicable.

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Multidimensional Structure–Activity Relationship of a Protein in Its Aggregated States

et al. 2010

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Gleich und doch sehr verschieden: Je nach den verwendeten chemischen, physikalischen und biologischen Bedingungen bildet ein einziges Protein fünf strukturell verschiedene Aggregate (siehe die Elektronenmikroskopiebilder, Maßstäbe: 500 nm), die alle das Kreuz‐β‐Faltblatt‐Motiv enthalten. Die Aggregate unterscheiden sich in ihrer Affinität zu Adenosin‐5′‐triphosphat, Thioflavin T, DNA und Membranmimetika sowie in ihrem Effekt auf die Zellgängigkeit.

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A New Amyloid-Like β-Aggregate with Amyloid Characteristics, Except Fibril Morphology

Cited by 24 publications

References 48 publications

Turn Nucleation Perturbs Amyloid β Self-Assembly and Cytotoxicity

Turn Nucleation Perturbs Amyloid β Self-Assembly and Cytotoxicity

Residue-Specific, Real-Time Characterization of Lag-Phase Species and Fibril Growth During Amyloid Formation: A Combined Fluorescence and IR Study of p-Cyanophenylalanine Analogs of Islet Amyloid Polypeptide

Multidimensional Structure–Activity Relationship of a Protein in Its Aggregated States

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