Molecular mechanism of Abeta recognition and neuroprotection by the glycoconjugate beta-sheet-breaker peptide Ac-LPFFD-Th

Inhibition of amyloid formation may represent a promising therapeutic approach for the treatment of neurodegenerative diseases. To this regard, peptide-based inhibitors of Abeta aggregation have been widely investigated with a particular emphasis to those derived from original amyloid sequences. The experimental work described in the present PhD Thesis aims at outlining the molecular mechanisms underlying the antifibrillogenic and neuroprotective action exhibited by a new class of trehalose conjugated pentapeptides. Trehalose (Th), a non-reducing disaccharide of alpha-(D)glucose, has been demonstrated to be effective in preventing the aggregation of several proteins. We figured out that the development of hybrid compounds may provide new molecules with improved properties that might sinergically increase the potency of their single moieties. Since it has been demonstrated that Abeta oligomers are the toxic species, it becomes a priority to counteract the Abeta self-assembly because of its doubly dangerous effect associated with oligomers generation and removal of the neurotrophic monomeric form of Abeta1-42 peptide. Starting from the well-known neuroprotective action of the LPFFD peptide, (C. Soto, Nat Med. 1998) we investigated whether the Ac-LPFFD-Th peptide would act as an Abeta monomer-stabilizer thus exerting a neuroprotective activity. In support of this hypothesis, time-resolved proteolysis and ESI-MS experiments, performed during my PhD experimental work, showed a direct interaction between these beta-breaker peptides and Abeta monomers. In this work, the C-terminal trehalose conjugated Ac-LPFFD-Th derivative ability to recognize and bind low molecular weight aggregated forms of Abeta has been investigated by means of different biophysical techniques, including Th-T fluorescence, DLS, ESI-MS and NMR. Furthermore, biological assays on murine cortical primary neuronal cultures were performed in order to clarify and further characterize the mechanism of cytoprotection exhibited by the Ac-LPFFD-Th. In this PhD thesis, we demonstrated that Ac-LPFFD-Th modifies the aggregation features of Abeta and protects neurons from Abeta oligomers toxic insult