Somatostatin, an In Vivo Binder to Aβ Oligomers, Binds to βPFOAβ(1-42) Tetramer

Abstract

Somatostatin (SST14) is strongly related to Alzheimers disease (AD), as its levels decline during aging, it regulates the proteolytic degradation of the amyloid beta peptide (A{beta}), and it binds to A{beta} oligomers in vivo. Recently, the 3D structure of a membrane-associated {beta}-sheet pore forming tetramer ({beta}PFOA{beta}(1-42) tetramer) has been reported. Here we show that SST14 binds selectively to the {beta}PFOA{beta}(1-42) tetramer without binding to monomeric A{beta}(1-42). Specific NMR chemical shift perturbations, observed during titration of SST14, define a binding site in the {beta}PFOA{beta}(1-42) tetramer and are in agreement with a 2:1 stoichiometry determined by both native MS and ITC. These results enabled us to perform driven docking and model the binding mode for the interaction. The present study provides additional evidence on the relation between SST14 and the amyloid cascade, as well as positions the {beta}PFOA{beta}(1-42) tetramer as a relevant aggregation form of A{beta} and as a potential target for AD.