A cell-based screen for inhibitors of intracellular Abeta aggregation

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There is an emerging consensus that non-fibrillar intracellular Abeta aggregates, rather than insoluble fibrils, are the most deleterious Abeta species and may play a central role in Alzheimer's disease (AD) pathogenesis. Thus, an attractive therapeutic approach to AD would be to seletively reduce the levels of potentially synaptotoxic Abeta aggregates by either stabilizing intracellular Abeta in its monomeric form or destabilizing the oligomeric structure. Low molecular weight drugs represent the most attractivetherapeutics for inhibiting Abeta aggregation as many small molecules are capable of permeating the blood-brain barrier (BBB) and crossing cell membranes. Historically, however, protein aggregation has been an extremely difficult target to address with synthetic drug-like molecules, owing in part to the large surface area generally covered by two interacting proteins and to the large, flat binding surfaces between the proteins. Another challenge is that while new types of organic compounds may be extremely potent when tested against isolated targets in the laboratory, they may cross-react with cellular components other than the desired target. Small molecules found in nature, often called 'natural products', typically have spent time inside of a cell during the course of evolution and are less likely to interact in a manner that damages cellular components such as membranes or DMA. In addition, it has been shown recently that many natural products are quite effective at inhibiting a diverse array of protein-protein interactions. Thus, an important question that we are exploring is whether natural products or natural product-like molecules can be isolated that effectively inhibit Abeta aggregation and, at the same time, be tolerated by living cells. The long-term goal of this research is to identify natural product-like inhibitors of intracellular Abeta aggregation that have potential as therapeutic agents for treating AD. Towards this goal, we have generated a cell-based assay for directly monitoring Abeta folding in the intracellular environment. This particular application seeks to: (1) configure our novel cell-based folding assay for high-throughput screening of combinatorial small-molecule libraries; and (2) isolate natural product-like compounds from diversity-oriented synthesis libraries that are capable of antagonizing Abeta aggregation. Such compounds will serve as leads for AD therapy and for biological studies that illuminate the physiological role of Abeta folding in mediating neurotoxicity.