Mutations in the microtubule-associated protein tau occur in some cases of inherited frontotemporal dementia (FTD), demonstrating that tau abnormalities can cause neurodegeneration. Many FTD mutations occur in regulatory elements that alter splicing and thereby expression of tau isoforms, rather than tau coding sequence. One of the hallmark neuropathologic features of AIzheimer's disease (AD) is the neurofibrillary tangle (NFT), which contains hyperphosphorylated tau. Characterization of the events that modify tau-associated neurodegenerative processes is critical for understanding the pathophysiology of AD, as well as FTD and related diseases, such as progressive supranuclear palsy and corticobasal degeneration, and for the development of therapeutics. In order to test the hypothesis that neurodegeneration can be caused by aberrant expression of wild-type tau, the longest isoform of human tau was overexpressed in the fruit fly, producing degeneration of the eye and underlying brain, but failing to produce neurofibrillary tangles. However, tau phosphorylation by co-expression of shaggy, the Drosophila homologue of glycogen synthase kinase (GSK)-3beta, an important tau kinase in vitro, produced a more severely degenerated eye, as well as lesions resembling NFT (Jackson, G.R., et al. (2002): Human wild-type tau interacts with wingless pathway components and produces neurofibrillary pathology in Drosophila. Neuron 34: 509-519). Here, we propose to test selected kinase inhibitors, caspase inhibitors, and antioxidants for their ability to suppress the dual tau + shaggy bioassay phenotype. We also will test a library of commercially available, FDA-approved compounds (Microsource Discovery Systems) for their ability to suppress the external eye phenotype of tau + shaggy flies. Subsequently, we will determine the effects of identified compounds on cell death and conformation and solubility of tau. This project contributes to the commitment of the UCLA Alzheimer's Disease Research Center (ADRC) to foster research that will lead to identification of disease-modifying therapies for AD and related conditions. The Project will interact with Project 2 assessing similar compounds in transgenic mice.
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