There are a large and diverse number of diseases that are commonly classified as conformational diseases. The common feature of these diseases is the rearrangement of a specific protein to a non-native conformation that promotes aggregation and deposition within tissues and/or cellular compartments. Such diseases include Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, amyloidoses, the prion encephalopathies, and many more. A common structural motif in the majority of these diseases is the emergence of extended, β-sheet rich, proteinaceous fibrillar aggregates that are commonly referred to as amyloids. These fibrillar species are comprised of intertwined protofibrillar filaments, which often have globular, soluble protein aggregate precursors, more commonly referred to as oligomers. For the vast majority of these diseases, there are no widely effective preventative or therapeutic treatments. The major research goal of our laboratory is to understand the molecular mechanisms that underlie neurodegenerative disorders associated with protein misfolding and aggregation, with a focus on Alzheimer’s disease and Huntington’s disease. In particular, we are interested in the potential role cellular and subcellular surfaces may play in these events.

We utilize a broad array of research tools and biochemical methods in our studies, but our primary tool is the atomic force microscope (AFM). AFM has provided particularly useful insights related to conformational disease due to its unique ability to be operated not only in air (ex situ) but also in solution (in situ), making it possible to directly visualize the behavior of biological macromolecules at solid-liquid interfaces, under nearly physiological conditions. The ultimate objective of our amyloidogenic peptide AFM studies is to elucidate the physiochemical aspects and molecular mechanisms of pathological self-assembly of biological macromolecules that lead to toxicity.

Research Topics

1. The role of surfaces and mutations in Aβ aggregation
   1. The major goal of the proposed work is to use a combination of ex situ and in situ atomic force microscopy (AFM) to characterize the structures and toxic biological properties of nanoscale aggregates formed by β-amyloid (Aβ) peptides containing various point mutations, which are implicated in variants of Alzheimer’s disease (AD). The role that cellular environment, and in particular surfaces, may play in dictating and stabilizing early oligomeric structures and the eventual formation of amyloid is poorly understood. We hypothesize that point mutations in Aβ alter the aggregation pathway and its interaction with cellular surfaces, resulting in different disease progression and phenotypes.
2. Aggregation of mutant huntingtin fragments and polyglutamine peptides
   1. The major goal of this project is to morphologically define the aggregation of expanded polyQ proteins, in particular huntingtin (htt), with a focus on the role of liquid/solid interfaces and protein context. Considering the numerous types of aggregates formed by proteins and peptides containing expanded polyQ tracts that can co-exist, the elucidation of toxic species is a daunting task. The co-existence of diverse aggregate types in heterogeneous mixtures further complicates this issue. We are obtaining a detailed understanding of the role of flanking sequences in influencing polyQ aggregation and a determination of the interaction of formed aggregates with cellular and subcellular surfaces associated with membranous organelles. Using a combination of ex situ and in situ AFM with other biochemical techniques, we are studying the aggregation of mutant htt exon1 proteins and synthetic polyQ peptides with various lengths of polyQ tracts and flanking sequences.