1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose Binds to the N-terminal Metal Binding Region to Inhibit Amyloid β-protein Oligomer and Fibril Formation.

The early oligomerization of amyloid β-protein (Aβ) is a crucial step in the etiology of Alzheimer's disease (AD), in which soluble and highly neurotoxic oligomers are produced and accumulated inside neurons. In search of therapeutic solutions for AD treatment and prevention, potent inhibitors that remodel Aβ assembly and prevent neurotoxic oligomer formation offer a promising approach. In particular, several polyphenolic compounds have shown anti-aggregation properties and good efficacy on inhibiting oligomeric amyloid formation. 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose is a large polyphenol that has been shown to be effective at inhibiting aggregation of full-length Aβ1-40 and Aβ1-42, but has the opposite effect on the C-terminal fragment Aβ25-35. Here, we use a combination of ion mobility coupled to mass spectrometry (IMS-MS), transmission electron microscopy (TEM) and molecular dynamics (MD) simulations to elucidate the inhibitory effect of PGG on aggregation of full-length Aβ1-40 and Aβ1-42. We show that PGG interacts strongly with these two peptides, especially in their N-terminal metal binding regions, and suppresses the formation of Aβ1-40 tetramer and Aβ1-42 dodecamer. By exploring multiple facets of polyphenol-amyloid interactions, we provide a molecular basis for the opposing effects of PGG on full-length Aβ and its C-terminal fragments.