Structure-function studies of key amyloid-degrading enzymes

Student thesis: Doctoral ThesisPhD

Abstract

The accumulation of the small peptide amyloid-β has been proposed as a major trigger for the development of Alzheimer’s disease. Within the brain, the concentration of amyloid-β is tightly controlled through production and clearance mechanisms. Studies have revealed that reduced levels of amyloid-β clearance are present in individuals living with Alzheimer’s disease which results in the observed accumulation of the peptide. This accumulation of amyloid-β can lead to the formation of large aggregated amyloid plaques - one of two detectable hallmarks of the disease.
Amyloid degrading enzymes (ADEs) are a group of proteins with the ability to degrade amyloid-β and are major players in the clearance of amyloid-β. Stimulating ADE activity or expression, in order to compensate for the decreased clearance in the Alzheimer’s disease phenotype, provides a promising therapeutic target. It has been reported in mice that upregulation of ADEs can reduce the levels of amyloid-β peptide and amyloid plaques – in some cases this led to improved cognitive function.
Among several known ADEs, neprilysin (NEP) and endothelin-converting enzyme I (ECE-1) have been identified to be two of the most potent. Both proteins have the capacity to digest soluble amyloid-β which, in turn, can form the toxic oligomeric species found within the brains of individuals living with Alzheimer’s disease. Whilst NEP and ECE-1 are known for their amyloid-degradation, they exhibit complexity through the additional substrates that they can degrade. Two such groups of substrates are the endothelins and natriuretic peptides. Both peptide groups are vasoactive and illustrate the strong link between NEP, ECE-1 and blood pressure regulation. The promiscuous nature of NEP and ECE-1 raises questions surrounding their specificity and how such a broad range of substrates can be degraded.
This research builds upon current structural and functional understanding of both NEP and ECE-1, giving a detailed insight into the molecular interactions that leads to the hydrolysis of peptide substrates. This research has used a cross-disciplinary approach of X-ray structure determination, mutagenesis and kinetic analysis in order to elucidate the crucial tasks performed by key ADEs.
Date of Award14 Oct 2020
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorVasanta Subramanian (Supervisor) & Ravi Acharya (Supervisor)

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