Abstract
The increase in life expectancy observed over the last century has led to the emergence of a new set of pathologies that constitutes a new threat for the world population. Among these pathologies, neurodegenerative diseases have gained an increased impact on society. Despite originating from different genetic, environmental and regulatory factors, many neurodegenerative disorders show similarities at sub-cellular and molecular levels. A characteristic common feature of ageing related diseases is the self‐assembly of misfolded proteins into neurotoxic oligomers and fibrils, which are resistant to degradation and lack the functionality of the native protein.Among these increasingly concerning diseases, Alzheimer’s disease (AD) affects over 80 individuals every day. Substantial epidemiological evidence shows an increased risk for developing AD in people affected by diabetes, which is associated with increased hyperglycaemia. The molecular mechanisms underlying the link between diabetes and AD remain elusive. For this reason, when approaching the study of AD, it is essential to consider the role that sugars play in disease development and, therefore, the role of post-translational modifications such as glycation. Contrary to glycosylation, glycation is an enzyme-free reaction that leads to attachment of a carbohydrate molecule to the protein and the formation of advanced glycation end-products (AGEs). Glycation is one of the pathological processes involved in diabetes and is thought to influence the structure of the islet amyloid polypeptide (IAPP), which plays a role in glycaemic regulation. Misfolded IAPP aggregates into toxic amyloid-like structures, very similar to the Abeta peptide (variants 1-40 and 1-42) deposits, often also heavily glycated, observed in AD patients.
The aim of this thesis is to unravel the effects of glycation on the structure and aggregation of the peptides IAPP and two of the most common variants of Abeta by means of an integrative structural approach.
Several biophysical techniques were employed to gain insights into the structural effects of glycation on the aggregation process of the IAPP and Abeta peptides. The occurrence and location of the glycation reaction was elucidated by mass spectrometry. The secondary structure variations upon glycation were observed by circular dichroism and nuclear magnetic resonance. Spectrofluorometric assays were employed to follow protein aggregation and glycation concomitantly. Finally, the morphological effects of glycation on amyloid fibrils were evaluated by high-resolution structural atomic force microscopy (AFM) studies.
| Date of Award | 1 Dec 2019 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Annalisa Pastore (Supervisor) & Rivka Isaacson (Supervisor) |