A common pathway for detergent-assisted oligomerization of Aß42.

Amyloid beta (Aß) aggregation is a slow process without seeding or assisted nucleation. Sodium dodecyl sulfate (SDS) micelles stabilize Aß42 small oligomers (in the dimer to tetramer range); subsequent SDS removal leads to a 150-kD Aß42 oligomer. Dodecylphosphorylcholine (DPC) micelles also stabilize an Aß42 tetramer. Here we investigate the detergent-assisted oligomerization pathway by solid-state NMR spectroscopy and molecular dynamics simulations. SDS- and DPC-induced oligomers have the same structure, implying a common oligomerization pathway. An antiparallel ß-sheet formed by the C-terminal region, the only stable structure in SDS and DPC micelles, is directly incorporated into the 150-kD oligomer. Three Gly residues (at positions 33, 37, and 38) create holes that are filled by the SDS and DPC hydrocarbon tails, thereby turning a potentially destabilizing feature into a stabilizing factor. These observations have implications for endogenous Aß aggregation at cellular interfaces.