Investigation of Two Potential Treatments for Frontotemporal Dementias by Mass Spectrometry

Intraneuronal tangles of the microtubule associated protein tau are a hallmark of frontotemporal dementia and other tauopathies. Tau stabilizes tubulin subunits to form microtubules in neuronal projections, but must be removed to allow transport vesicles to pass. This dynamic process is controlled by the phosphorylation state of tau; increased phosphorylation removes tau from the microtubule. Unbound tau aggregates and is unable to be cleared, so a small molecule inhibitor of aggregation could stop the progression of the pathology. The van Breemen lab has access to various natural product fractions prepared by collaborating research groups and are not widely available. The previously published tau aggregation inhibitions screening assay utilized a fluorescence detector, which can only screen single molecule samples. A mass spectrometry based screen was developed to be able to screen natural product fractions, which is described in Chapter 2. Natural product fractions obtained from marine actinomycetes were screened in Chapter 3 and hit fractions were identified. The three fractions which inhibited aggregation were profiled using a metabolomics approach, which is described in Chapter 4. The identification and structure elucidation of a small amount of natural product is the most difficult step, so this approach moves it to the end to minimize the number of compounds that need to be identified. The actinomycetes need to be recultured, taking several months, so the profiles of the new and old fractions can be compared to confirm the same compounds are present. The 5-HT6 receptor antagonist, PRX-07034 is a potential treatment for memory issues related to frontotemporal dementias. Chapter 5 outlines a validated UHPLC-MS-MS method to quantitate the compound in both rat serum and brain. The behavioral effects of the treatment have been studied for nearly 10 years; however the compound was never analytically determined to reach the brain