Synthesis and characterization of stapled peptides inspired by the EF helix of TTR

One of the most common forms of senile dementia is Alzheimer's disease, a neurodegenerative disorder that causes progressive memory loss and cognitive decline. Experimental evidence has identified several factors responsible for the progression of the syndrome, including reduced acetylcholine levels, metal dyshomeostasis in the nervous system, and oxidative stress. In addition, the formation of insoluble fibrillar amyloid aggregates of β-amyloid and neurofibrillary tangles of tau protein, extracellular and intracellular respectively, are considered the hallmark of this disease. β-Amyloid plaques are reported to be the main drivers of disease progression and are formed as a result of negative protein-protein interactions, which trigger pro-aggregatory cascades and lead to the inhibition of degradation mechanisms. Transthyretin (TTR) is an endogenous homotetrameric protein with amyloid potential, capable of interacting positively with β-amyloid oligomers and fibrils, inhibiting their aggregation and promoting their degradation, acting as a neuroprotective factor. Scientific evidence shows that conformational changes in TTR in the presence of iron, manganese and zinc transform the protein into a metalloprotease capable of degrading β-amyloid fibrils. Conversely, copper does not confer this proteolytic activity to the protein but has been shown to mediate the stabilisation of the TTR-β-amyloid complex. The aim of the project is to synthesise peptide-mimetic foldamers inspired by the alpha-helical portion of TTR (residues 74-83), identified as the hot spot of the interaction. The foldameri mimic the hot spot of the cross-interaction between TTR and β-amyloid, in order to obtain a correct interpretation of the mechanism and the possibility of designing amyloid aggregation inhibitors that are potentially applicable in a therapeutic context. Based on the above evidence, peptide sequences inspired by the alpha-helix sequence of TTR were synthesised using solid-phase peptide synthesis (SPPS) protocols: a) Sequence carrying a copper-chelating amino acid, intended for lactam cyclisation b) Sequence intended for the exploration of cyclisation via manganese-catalysed C-H activation c) Sequence used for the C-H activation approach approved on a peptide model in the context of insulin, as a comparison with TTR as a potential chaperone protein.