Characterization of Intermediate Steps in Amyloid Beta (Aβ) Production under Near-native Conditions

Abstract

Background:The 42 amino acid long amyloid beta peptide (A␤42) plays a pivotal role in Alzheimer disease. Results: A novel assay was developed and enabled us to describe the process of 〈␤42 production and modulation. Conclusion: A␤42 is generated through different pathways, which are differently affected by disease causing mutations and anti-amyloidogenic drugs. Significance: The data provide key information for therapeutic development in Alzheimer disease.

Amyloid Precursor Protein (APP) Metabolites APP Intracellular Fragment (AICD), Aβ42, and Tau in Nuclear Roles

“…An alternative cleavage occurs and generates AICD49 -99, which is N-terminally extended by one amino acid that begins at Leu-49 according to A␤ numbering, which is in agreement with the detection of A␤48 and molecules of the A␤42 peptide series (49,50). Overall, it is clear that ⑀-cleavage is a limiting step for the subsequent ␥-secretase ␥-cuts.…”

“…The main cleavage sites of ␣-, ␤-, and ␥-secretases are indicated by the respective Greek letters, the APP transmembrane sequence (TMS) is highlighted in yellow, the amino acid numbers are referring to the A␤ sequence, and the blue bar indicates residues of A␤42. The multiple cleavages indicated by arrows and numbers occur from the C-to the N-terminal direction in a precursor-product cascade exerted by the ␥-secretase complex (49,50). The major processing routes converge at A␤34, which is further hydrolyzed into A␤30 (50).…”

“…The multiple cleavages indicated by arrows and numbers occur from the C-to the N-terminal direction in a precursor-product cascade exerted by the ␥-secretase complex (49,50). The major processing routes converge at A␤34, which is further hydrolyzed into A␤30 (50). The N-terminal half of the TMS of APP is stabilized the GXXXG interaction motif with Gly-29 and Gly-33 (in red) as the central residues (51,96,97).…”

Amyloid beta: structure, biology and structure-based therapeutic development

“…The amyloidogenic processing of APP thus involves sequential cleavages by β-and γ-secretase at the N and C termini of Aβ, respectively ( Figure 2) [17] . The 99-amino-acid C-terminal fragment of APP (C99 ) generated by β-secretase cleavage can be internalized and further processed by γ-secretase at multiple sites to produce cleavage fragments of 43,45,46,48,49 and 51 amino acids that are further cleaved to the main final Aβ forms, the 40-amino-acid Aβ40 and the 42-amino-acid Aβ42, in endocytic compartments [18,19] . The cleavage of C99 by γ-secretase liberates an APP intracellular domain (AICD) that can translocate to the nucleus, where it may regulate gene expression, including the induction of apoptotic genes.…”

“…Approximately 25% of the surface is uninterruptedly hydrophobic, and the compact coil structure is meta-stable, which may lead to a global conformational rearrangement and the formation of an intermolecular beta-sheet secondary structure caused by fibrillization. The 3D NMR structures of Aβ peptide (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) and Aβ peptide (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) show two helical regions connected by a regular type I β-turn. Aβ peptide (25-35) is a highly toxic synthetic derivative of Aβ peptides.…”