Grant: Alliance Grants

Many neurodegenerative diseases (NDDs) involve the accumulation in neurons of aggregates made of specific proteins. Inhibiting or clearing such aggregates has been a major strategy for developing NDD therapeutics. However, the small oligomers that are the most neurotoxic aggregates are very difficult to detect. Drug-discovery efforts thus typically rely on assays that are sensitive only to large aggregates, even though the latter are less relevant to disease. The effects of potential aggregation-inhibiting drug candidates on the toxic small oligomers are then deduced indirectly from observations of larger aggre-gates, an approach whose reliability is not well established. Better assays of small oligomers are thus urgently needed. Single-molecule mass photometry (SMMP), which measures the mass of individual protein particles via interferometric light scattering, offers a possible solution. We recently showed that SMMP is a powerful tool for directly monitoring small oligomer populations, able to count the populations of each distinct oligomer size in real time and watch how they all evolve. However, SMMP has not yet been used to test the effects of aggregation inhibitors on small oligomers directly-the application that is of particular interest for drug discovery. Here we propose to demonstrate the practical utility of SMMP as a drug-discovery tool by using it (1) to characterize the oligomerization kinetics for several NDD-related proteins, (2) to show that SMMP can reveal how aggregation inhibitors change oligomerization mecha-nisms, and (3) to test how well assays of large aggregates capture the kinetics of small oligomers. The outcome of the project will be protocols for deploying SMMP in drug-discovery applications that will be of general utility to the pharmaceutical industry.