Alzheimer's Disease (AD) is a debilitating mental disorder involving severe cognitive impairment. Over 10 million people have AD, costing society $350 billion. A drug that could effectively teat AD would be worth $50 billion. Presently, there is no effective treatment of AD. The neuropathology of AD involves plaque formation in the brain and neuronal death. The lesions are believed to be caused by the neurotoxic agent beta-peptide which is proteolytically derived from a polypeptide precusor, amyloid precusor protein (APP). Beta-peptide is produced from APP by proteases known as secretases. Inhibitors of secretase activity and beta-peptide production could block the progression of the disease and the cognitive dysfunctions, but such inhibitors have not been developed because authentic secretases have not been identified. Dr. Vivian Hook, the consultant of the project, and collaborators have discovered cells that naturally produce beta-peptide, and found that subcellular organelles from these cells contain the authentic secretases. These organelles can be purified so that only irrelevant proteolytic activities in other cellular compartments can be reduced. The PI and coworkers have developed a highly sensitive fluorescent secretase assay using the lysate of such organelles and peptide substrates containing the secretase recognition sites to measure beta- and gamma secretase activities. In this proposal, they will develop and optimize these assays to achieve sensitive, reproducible, and rapid secretase assays that will allow use of theses assays in future high throughput screening of combinatorial libraries for the discovery of compounds that inhibit beta-peptide production. This project will also test commercially available protease inhibitors to demonstrate that such secreatase assays can effectively detect inhibitors, and to assess whether beta- and gamma-secretase activities may represent similar or distinct drug targets. These authentic secretase assays will be essential for development of drugs to improve the mental health of AD patients.
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