Cell-Derived Hexameric β-Amyloid: A Novel Insight Into Composition, Self-Assembly and Nucleating Properties

Abstract A key hallmark of Alzheimer’s disease (AD) is the extracellular deposition of amyloid plaques composed primarily of the amyloidogenic amyloid-β (Aβ) peptide. The Aβ peptide is a product of sequential cleavage of the Amyloid Precursor Protein (APP), the first step of which gives rise to a C-terminal Fragment (C99). Cleavage of C99 by γ-secretase activity releases Aβ of several lengths and the Aβ42 isoform in particular has been identified as being neurotoxic. The misfolding of Aβ leads to subsequent amyloid fibril formation by nucleated polymerisation. This requires an initial and critical nucleus for self-assembly. Here, we identify and characterise the composition and self-assembly properties of cell-derived hexameric Aβ42 and show its nucleating properties which are dependent on the Aβ monomer availability. Identification of nucleating assemblies that contribute to self-assembly in this way may serve as therapeutic targets to prevent the formation of toxic oligomers.

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Cell-derived hexameric β-amyloid: a novel insight into composition, self-assembly and nucleating properties

10.1101/2020.12.15.422916 ◽

2020 ◽

Author(s):

Devkee M Vadukul ◽

Céline Vrancx ◽

Pierre Burguet ◽

Sabrina Contino ◽

Nuria Suelves ◽

...

Keyword(s):

Self Assembly ◽

Critical Nucleus ◽

Amyloid Fibril ◽

Amyloid Β ◽

Aβ Peptide ◽

Amyloid A ◽

Amyloid Fibril Formation ◽

Secretase Activity ◽

Β Amyloid ◽

Insight Into

A key hallmark of Alzheimer's disease (AD) is the extracellular deposition of amyloid plaques composed primarily of the amyloidogenic amyloid-β (Aβ) peptide. The Aβ peptide is a product of sequential cleavage of the Amyloid Precursor Protein (APP), the first step of which gives rise to a C-terminal Fragment (C99). Cleavage of C99 by γ-secretase activity releases Aβ of several lengths and the Aβ42 isoform in particular has been identified as being neurotoxic. The misfolding of Aβ leads to subsequent amyloid fibril formation by nucleated polymerisation. This requires an initial and critical nucleus for self-assembly. Here, we identify and characterise the composition and self-assembly properties of cell-derived hexameric Aβ42 and show its nucleating properties which are dependent on the Aβ monomer availability. Identification of nucleating assemblies that contribute to self-assembly in this way may serve as therapeutic targets to prevent the formation of toxic oligomers.

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An evaluation of the self-assembly enhancing properties of cell-derived hexameric amyloid-β

Scientific Reports ◽

10.1038/s41598-021-90680-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Devkee M. Vadukul ◽

Céline Vrancx ◽

Pierre Burguet ◽

Sabrina Contino ◽

Nuria Suelves ◽

...

Keyword(s):

Amyloid Precursor Protein ◽

Self Assembly ◽

Critical Nucleus ◽

Amyloid Fibril ◽

Amyloid Β ◽

Amyloid Plaques ◽

The Self ◽

Aβ Peptide ◽

Amyloid Fibril Formation ◽

Secretase Activity

AbstractA key hallmark of Alzheimer’s disease is the extracellular deposition of amyloid plaques composed primarily of the amyloidogenic amyloid-β (Aβ) peptide. The Aβ peptide is a product of sequential cleavage of the Amyloid Precursor Protein, the first step of which gives rise to a C-terminal Fragment (C99). Cleavage of C99 by γ-secretase activity releases Aβ of several lengths and the Aβ42 isoform in particular has been identified as being neurotoxic. The misfolding of Aβ leads to subsequent amyloid fibril formation by nucleated polymerisation. This requires an initial and critical nucleus for self-assembly. Here, we identify and characterise the composition and self-assembly properties of cell-derived hexameric Aβ42 and show its assembly enhancing properties which are dependent on the Aβ monomer availability. Identification of nucleating assemblies that contribute to self-assembly in this way may serve as therapeutic targets to prevent the formation of toxic oligomers.

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The amphibian antimicrobial peptide uperin 3.5 is a cross-α/cross-β chameleon functional amyloid

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2014442118 ◽

2021 ◽

Vol 118 (3) ◽

pp. e2014442118

Author(s):

Nir Salinas ◽

Einav Tayeb-Fligelman ◽

Massimo D. Sammito ◽

Daniel Bloch ◽

Raz Jelinek ◽

...

Keyword(s):

Antimicrobial Peptide ◽

Amyloid Fibrils ◽

Amyloid Fibril ◽

Membrane Damage ◽

Fibril Formation ◽

Regulation Mechanism ◽

Bacterial Cells ◽

Amyloid Fibril Formation ◽

Β Amyloid ◽

Β Sheets

Antimicrobial activity is being increasingly linked to amyloid fibril formation, suggesting physiological roles for some human amyloids, which have historically been viewed as strictly pathological agents. This work reports on formation of functional cross-α amyloid fibrils of the amphibian antimicrobial peptide uperin 3.5 at atomic resolution, an architecture initially discovered in the bacterial PSMα3 cytotoxin. The fibrils of uperin 3.5 and PSMα3 comprised antiparallel and parallel helical sheets, respectively, recapitulating properties of β-sheets. Uperin 3.5 demonstrated chameleon properties of a secondary structure switch, forming mostly cross-β fibrils in the absence of lipids. Uperin 3.5 helical fibril formation was largely induced by, and formed on, bacterial cells or membrane mimetics, and led to membrane damage and cell death. These findings suggest a regulation mechanism, which includes storage of inactive peptides as well as environmentally induced activation of uperin 3.5, via chameleon cross-α/β amyloid fibrils.

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Structural requirements of glycosaminoglycans for facilitating amyloid fibril formation of human serum amyloid A

Amyloid ◽

10.3109/13506129.2016.1168292 ◽

2016 ◽

Vol 23 (2) ◽

pp. 67-75 ◽

Cited By ~ 11

Author(s):

Hiroka Takase ◽

Masafumi Tanaka ◽

Aki Yamamoto ◽

Shiori Watanabe ◽

Sanae Takahashi ◽

...

Keyword(s):

Human Serum ◽

Serum Amyloid A ◽

Amyloid Fibril ◽

Fibril Formation ◽

Serum Amyloid ◽

Structural Requirements ◽

Amyloid A ◽

Amyloid Fibril Formation

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A pH-dependent conformational transition of Aβ peptide and physicochemical properties of the conformers in the glial cell

Biochemical Journal ◽

10.1042/bj3610547 ◽

2002 ◽

Vol 361 (3) ◽

pp. 547-556 ◽

Cited By ~ 13

Author(s):

Yoichi MATSUNAGA ◽

Nobuhiro SAITO ◽

Akihiro FUJII ◽

Junichi YOKOTANI ◽

Tadakazu TAKAKURA ◽

...

Keyword(s):

Glial Cell ◽

Conformational Changes ◽

Conformational Transition ◽

Early Stage ◽

Ph Dependence ◽

Amyloid Β ◽

Proteinase K ◽

Aβ Peptide ◽

Ph Dependent ◽

Insight Into

In the present study we identified the epitopes of antibodies against amyloid β-(1–42)-peptide (Aβ1–42): 4G8 reacted with peptides corresponding to residues 17–21, 6F/3D reacted with peptides corresponding to residues 9–14, and anti 5-10 reacted with peptides corresponding to residues 5–10. The study also yielded some insight into the Aβ1–42 structures resulting from differences in pH. An ELISA study using monoclonal antibodies showed that pH-dependent conformational changes occur in the 6F/3D and 4G8 epitopes modified at pH 4.6, but not in the sequences recognized by anti 1-7 and anti 5-10. This was unique to Aβ1–40 and Aβ1–42 and did not occur with Aβ1–16 or Aβ17–42. The reactivity profile of 4G8 was not affected by blockage of histidine residues of pH-modified Aβ1–40 and Aβ1–42 with diethyl pyrocarbonate; however, the mutant [Gln11]Aβ1–40 abrogated the unique pH-dependence towards 4G8 observed with Aβ1–40. These findings suggest that these epitopes are cryptic at pH4.6, and that Glu11 is responsible for the changes. We suggest that the abnormal folding of 6F/3D epitope affected by pH masked the 4G8 epitope. A study of the binding of metal ions to Aβ1–42 suggested that Cu2+ and Zn2+ induced a conformational transition around the 6F/3D region at pH7.4, but did not affect the region when it was modified at pH4.6. However, Fe2+ had no effect, irrespective of pH. Aβ modified at pH 4.6 appeared to be relatively resistant to proteinase K compared with Aβs modified at pH7.4, and the former might be preferentially internalized and accumulated in a human glial cell. Our findings suggest the importance of microenvironmental changes, such as pH, in the early stage of formation of Aβ aggregates in the glial cell.

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The Tottori (D7N) and English (H6R) Familial Alzheimer Disease Mutations Accelerate Aβ Fibril Formation without Increasing Protofibril Formation

Journal of Biological Chemistry ◽

10.1074/jbc.m608220200 ◽

2006 ◽

Vol 282 (7) ◽

pp. 4916-4923 ◽

Cited By ~ 77

Author(s):

Yukiko Hori ◽

Tadafumi Hashimoto ◽

Yosuke Wakutani ◽

Katsuya Urakami ◽

Kenji Nakashima ◽

...

Keyword(s):

Alzheimer Disease ◽

Amyloid Fibril ◽

Amyloid Β ◽

Fibril Formation ◽

Amyloid Β Protein ◽

Protein Precursor ◽

Amyloid Fibril Formation ◽

Β Protein ◽

Familial Alzheimer Disease ◽

Aβ Production

A subset of Alzheimer disease cases is caused by autosomal dominant mutations in genes encoding the amyloid β-protein precursor or presenilins. Whereas some amyloid β-protein precursor mutations alter its metabolism through effects on Aβ production, the pathogenic effects of those that alter amino acid residues within the Aβ sequence are not fully understood. Here we examined the biophysical effects of two recently described intra-Aβ mutations linked to early-onset familial Alzheimer disease, the D7N Tottori-Japanese and H6R English mutations. Although these mutations do not affect Aβ production, synthetic Aβ(1-42) peptides carrying D7N or H6R substitutions show enhanced fibril formation. In vitro analysis using Aβ(1-40)-based mutant peptides reveal that D7N or H6R mutations do not accelerate the nucleation phase but selectively promote the elongation phase of amyloid fibril formation. Notably, the levels of protofibrils generated from D7N or H6R Aβ were markedly inhibited despite enhanced fibril formation. These N-terminal Aβ mutations may accelerate amyloid fibril formation by a unique mechanism causing structural changes of Aβ peptides, specifically promoting the elongation process of amyloid fibrils without increasing metastable intermediates.

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