Seeded growth of β-amyloid fibrils from Alzheimer's brain-derived fibrils produces a distinct fibril structure

Abstract

Studies by solid-state nuclear magnetic resonance (NMR) of amyloid fibrils prepared in vitro from synthetic 40-residue ␤-amyloid (A␤ 1-40) peptides have shown that the molecular structure of A␤1-40 fibrils is not uniquely determined by amino acid sequence. Instead, the fibril structure depends on the precise details of growth conditions. The molecular structures of ␤-amyloid fibrils that develop in Alzheimer's disease (AD) are therefore uncertain. We demonstrate through thioflavin T fluorescence and electron microscopy that fibrils extracted from brain tissue of deceased AD patients can be used to seed the growth of synthetic A␤ 1-40 fibrils, allowing preparation of fibrils with isotopic labeling and in sufficient quantities for solid-state NMR and other measurements. Because amyloid structures propagate themselves in seeded growth, as shown in previous studies, the molecular structures of brain-seeded synthetic A␤ 1-40 fibrils most likely reflect structures that are present in AD brain. Solid-state 13 C NMR spectra of fibril samples seeded with brain material from two AD patients were found to be nearly identical, indicating the same molecular structures. Spectra of an unseeded control sample indicate greater structural heterogeneity. 13 C chemical shifts and other NMR data indicate that the predominant molecular structure in brain-seeded fibrils differs from the structures of purely synthetic A␤1-40 fibrils that have been characterized in detail previously. These results demonstrate a new approach to detailed structural characterization of amyloid fibrils that develop in human tissue, and to investigations of possible correlations between fibril structure and the degree of cognitive impairment and neurodegeneration in AD.Alzheimer's disease ͉ electron microscopy ͉ solid-state nuclear magnetic resonance

Seeded strain‐like transmission of β‐amyloid morphotypes in APP transgenic mice

“…In apparent contrast, previous in vitro studies have reported that assemblies of Ab protofibrils with different Ab40/42 ratios have similar molecular structures [27,28]. However, in vivo and within a cellular environment Ab aggregation is likely different [10]. While the present study only focused on Ab40 and Ab42, it should be noted that there are many additional Ab isoforms with various amino-and carboxy terminal lengths.…”

Antiparallel β-sheet architecture in Iowa-mutant β-amyloid fibrils

“…2C), possibly indicating comparable populations of two F19 side-chain conformations. The 13 C linewidths of 1.6-2.3 ppm full-width-at-halfmaximum are larger than in spectra of WT-Aβ 1-40 and D23N-Aβ 1-40 fibrils that contain in-register parallel β-sheets (13,14,16), reflecting a greater degree of internal disorder in SFg2 fibrils that may be associated with their greater curvature. Fig.…”

“…Experimental results for Aβ 1-40 (6,8,10,11,13,14), Aβ 1-42 (5, 6, 9), Aβ 10-35 (1, 9), α-synuclein (22), amylin (20,21), β 2 -microglobulin (23,24), Ure2p (27), Sup35 (26), and PrP (28,29) fibrils support the idea that in-register parallel β-sheets might be a universal structural feature of amyloid fibrils when they are formed by full-length peptides and proteins. For HET-s fibrils, a "quasi-in-register" parallel β-sheet structure was also found, with homologous protein segments forming a parallel cross-β motif (48).…”

“…Antiparallel β-sheets with odd values of N-M occur in fibrils formed by residues 11-25 of Aβ (Aβ [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], where the registry is 17 þ k ↔ 20 − k at pH 7.4 and 17 þ k ↔ 22 − k at pH 2.4 (31). SSNMR spectra of Aβ 11-25 fibrils show sharp lines and single sets of chemical shifts, indicating high symmetry (i.e., one molecule in the asymmetric unit).…”

“…Numerous structural studies of Aβ fibrils and oligomers have been reported (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), motivated by the dual goals of contributing to preventive and therapeutic approaches to AD and of elucidating the biophysical basis for amyloid formation. A defining structural characteristic of an amyloid fibril is the presence of a cross-β motif; i.e., a ribbon-like β-sheet running the length of the fibril, with β-strands approximately perpendicular to and interstrand hydrogen bonds approximately parallel to the long fibril axis.…”