Both mice and humans have amyloid-like polyglutamine fibrils in the nucleus of neurons that appear to cause the disease. This finding is interesting, because huntingtin is a cytoplasmic protein, not a nuclear protein. We use analytical ultracentrifugation and mass spectrometry to study the changes in quaternary structure and circular dichroism, fluorescence, and nuclear magnetic resonance spectroscopy to investigate the changes in tertiary structure required for formation of amyloid fibrils. We now know that significant changes in tertiary structure are required for the conversion of these proteins into amyloid. The challenge remaining is to understand the details of these changes, the dynamic properties of the intermediates, and the self-assembly mechanism that yields amyloid.
Most likely amyloid causes toxic effects through multiple mechanisms.
We have embarked on a project to understand why amyloid fibrils kill nerve cells. Specifically, we have prepared fluorescently labeled amyloid and glutamine polypeptides to understand the fate of these molecules in cells. Recent cocrystal structures of the normally folded form of transthyretin with second-generation inhibitors suggest new molecules to synthesize and test. Our philosophy is to develop simple parallel syntheses that can be used to prepare libraries to quickly sort out structure-activity relationships. The genetic selection system under development for the detection of inhibitors of polyglutamine aggregation and an increasing synthetic effort should provide therapeutic solutions to Huntington's disease, which may also be an amyloid-like disease.