Protein-Folding and Aggregation

The study of amyloid structure and growth has been motivated by their implication in many human diseases. There are more than 20 diseases associated with excessive deposits of amyloid plaques in the affected tissue or organ including Alzheimer's disease (AD), Parkinson's disease (PD), type II diabetes, and spongiform encephalopathies. 

In these disease states, proteins that are normally soluble undergo aggregation to form various intermediates and amyloidogenic species. These species subsequently assemble to generate insoluble fibrils that accumulate in the affected tissues or organs. A detailed understanding of amyloid growth mechanisms will allow new approaches to the prevention of amyloid formation and better diagnostics for early detection of amyloidogenic diseases. 

A molecular-level mechanism of how the different amyloid species interconvert is the goal of this project. There are many species of amyloid particles present physiologically. Our single molecule studies aim to classify the species involved in amyloid formation according to size, shape, kinetic reactivity, and monomer 2° and 3° structural information. A molecular-level mechanism of amyloid growth must include details as to when the protein misfold occurs and how it is influenced by the dynamics of protein structure. To determine the physical interactions and structural changes involved in the amyloid assembly mechanism, we study effect of environmental variables such as temperature, pH, helix promoting solvents, denaturants, and reducing agents. The environmental effect on aggregation is expected to be species-dependent reflecting a possible hierarchy of structural interactions.

Recently the Talaga Lab has found that the initiation of amyloidogenic aggregation in alpha-synuclein occurs at hydrophobic interfaces and does not occur in their absence. The data is consistent with the initial dimerization being the step activated by association of alpha-synuclein with the hydrophobic interface. Given the association of alpha-synuclein amyloidogenesis with the progression of Parkinson's Disease, the Talaga Lab is seeking to continue these studies to determine what conditions, if any, can induce amyloid formation in the absence of hydrophobic interfaces. The Talaga Lab is also investigating the nature of the association of alpha-synuclein with the interface to determine the relevant sequence and condition determinants on the heterogeneous initiation process.