Irreversible dimerization/tetramerization and post-translational modifications inhibit proteolytic degradation of Aβ peptides of Alzheimer's disease

Experimental evidence increasingly implicates the β-amyloid peptide in the pathogenesis of Alzheimer's disease. β-amyloid filaments dramatically accumulate in the neuritic plaques and vascular deposits as the result of the brain's inability to clear these structures. In this paper, we demonstrate that in addition to the intrinsic stability of AβN-42, the time dependent generation of irreversibly associated Aβ dimers and tetramers incorporated into Aβ filaments are themselves resistant to proteolytic degradation. The presence of post-translational modifications such as isomerization of aspartyls 1 and 7, cyclization of glutamyl 3 to pyroglutamyl and oxidation of methionyl 35, further contribute to the insolubility and stability of Aβ. All these factors promote the accumulation of neurotoxic amyloid in the brains of patients with Alzheimer's disease, and should be considered in therapeutic strategies directed towards the dissociation of the brain's Aβ filaments. Copyright (C) 1998 Elsevier Science B.V.