An investigation of the ABAD-Aβ interaction as a potential therapeutic target for the treatment of Alzheimer’s disease

Abstract

Alzheimer’s disease (AD) is the leading cause of dementia but despite being identified over a century ago, current treatments remain limited. To date, no disease-modifying therapies are available. Soluble, intracellular forms of β-amyloid (Aβ), a protein associated with AD, have been identified and intracellular targets of Aβ are being investigated as potential targets for new drugs. Amyloid binding alcohol dehydrogenase (ABAD) was previously identified as a mitochondrial target of Aβ and is known to be up-regulated in AD. This interaction results in production of reactive oxygen species and cell death. Using a small peptide, known as the “decoy peptide”, disruption of this interaction has been shown to reverse biochemical and behavioural symptoms in an AD mouse model. The work reported in this thesis describes the approaches taken to develop methods for in vitro and ex vivo study of the interaction between ABAD and Aβ. A fluorogenic assay for measuring the intracellular activity of ABAD in living cells was developed and using this technique, the intracellular inhibition of ABAD by Aβ was observed for the first time. Surface plasmon resonance was used to measure binding between ABAD and Aβ and also showed the first quantitative analysis of direct binding of the decoy peptide to Aβ42. In order to synthesise small molecule inhibitors of ABAD activity with the aim of developing a molecular probe of the enzyme’s activity, compounds were identified by screening a fragment-based library. Subsequent optimisation of the compound structure led to a 10-fold improvement in the IC50 and has resulted in a lead compound for future development. A similar screening strategy was employed to identify potential small molecule inhibitors of the ABAD-Aβ interaction. This research has resulted in a range of tools and methods for studying ABAD activity and interactions, which will greatly benefit future work on developing compounds that inhibit the ABAD-Aβ interaction to provide a novel method for treating Alzheimer’s disease.