Abstracts Category : Other

Self-oligomerization of the hydrophobic regions within amyloid beta and prion protein

by Shaon Basu

Proteinopathies of the central nervous system (CNS) encompass a broad range of disorders (Alzheimer, Parkinson, Huntington and prion diseases) which invariably lead to human neurodegeneration. Such diseases bear a heavy financial burden on healthcare and elevate socio-economic costs, and will continue to do so as the general population ages. In our current predicament, there is a lack in etiological treatments for such diseases, rendering them incurable and unpreventable. Consensus in the field of translational research has attributed disease pathology to the misfolding and aggregation of certain proteins. The work in this thesis examines two highly aggregating proteins found in Alzheimer and Prion diseases, beta amyloid (A) and prion protein (PrP) respectively, in efforts to assist in the development of rationally designed therapies. Intriguingly, both proteins possess highly hydrophobic stretches rich in small amino acids such as glycine (G) and alanine (A), which can organize to form motifs that determine their synthesis, trafficking, folding, processing and degradation in cells. The guiding hypothesis is that such regions in these proteins may provide for a valid molecular target for therapeutic intervention.Recently, a human mutation within the highly conserved hydrophobic region of PrP (glycine 127 exchanged to valine) was characterized to confer complete neuroprotection from infectious prions. Similarly, other familial mutations and polymorphisms which exist in this very region have been shown to elicit or potentiate various prion disease phenotypes. Interestingly, of the mutations cataloged to date, the pathogenic and protective mutations seem to exist separately at two distinct motifs within the hydrophobic region of PrP: namely its N-terminal AGAAAAGA palindrome and C-terminal GxxxG-like motifs. In efforts to understand how such mutations alter the behavior of PrP, I examined their effects on oligomerization of the hydrophobic region within the lipid bilayer environment. As the entirety of the region is heavily implicated in the biogenesis and misfolding of PrP, the findings described here may help provide mechanistic insight on how one could develop a therapeutic agent that could target these motifs to exert effects much like the G127V mutation. Like PrP, A also possesses a hydrophobic region notorious for aggregation and involvement in neurodegeneration. This region also contains a triple repeat GxxxG motif, which has been dually implicated in the biogenesis and toxicity of A peptides. As such, I have examined certain compounds that can modulate generation of these peptides (-secretase modulators), to examine if they can interact with GxxxG motifs to elicit their therapeutic effects. In addition to this, I have also developed a facile method for the production of the most toxic and highly aggregating A species, A 1 - 42. As synthetically derived A counterparts have lower toxicity, slower aggregation kinetics, and are commercially inflated in price, this production method for recombinant A willAdvisors/Committee Members: Gerhard Multhaup (Internal/Supervisor).