20S proteasome activation as an innovative therapeutic strategy

Accumulation and aggregation of intrinsically disordered proteins (IDPs), such as Îł-synuclein, amyloid Îø, and tau, is associated with the pathogenesis of several neurodegenerative diseases, including Parkinson's disease and Alzheimer's disease. The 20S proteasome is the primary protease charged with regulating cellular levels of IDPs, but as humans age these proteins can become dysregulated resulting in their accumulation and aggregation seen in neurodegenerative diseases. Although the pathogenesis of these neurodegenerative diseases is still under intense investigation, it has been shown that the oligomeric forms of IDPs, including Îł-synuclein and amyloid Îø, are toxic to neurons and can impair proteasome function. This leads to additional accumulation of the IDPs, further promoting disease progression. Additionally, IDPs released by degenerating neurons activate the native immune cells of the brain, microglia, and induce their activation. These activated microglia release pro-inflammatory signaling molecules, which when coupled with continued IDP accumulation and release results in chronic neuroinflammation, contributing to further neuron degeneration.The Tepe Lab aims to develop small molecule activators of the 20S proteasome that enhance its ability to degrade IDPs, thus assisting in the prevention of their further accumulation and aggregation. We propose that these small molecule 20S proteasome activators represent a novel therapeutic method by which we may impede neurodegenerative disease progression. Here, I report the identification of novel small molecule 20S proteasome activator scaffolds that selectively enhance 20S proteasome activity. These activators enhance 20S-mediated degradation of IDPs that are implicated in neurodegenerative disease development. The identification of these novel activator scaffolds will enhance the chance of success while developing this novel therapeutic strategy and permit development of additional analogues with promising activities and drug-like properties. With these activators in hand, several novel methods were developed that demonstrate the potential of small molecule 20S proteasome activation as an innovative therapeutic strategy for combating neurodegenerative diseases. It was demonstrated for the first time that small molecule activators can protect against inhibition of the 20S proteasome by IDP oligomers associated with neurodegenerative disease pathogenesis and that these oligomers can be reduced through 20S proteasome activation in vitro. These results suggest that small molecule 20S proteasome activation has the potential to assist in re-establishing proteostasis in diseased neurons. Additionally, it was found that small molecule 20S proteasome activators can counteract the accumulation of an overexpressed familial Parkinson's disease related IDP, A53T Îł-synuclein, in cells. This demonstrated that this method shows promise for translation into cellular systems. As such, additional cellular models were conceived, and their development initiated to generate more disease relevant models for further evaluating this method. Finally, small molecule 20S proteasome activators were found to reduce IDP-induced release of the pro-inflammatory cytokine TNF-Îł by microglia. Thus, this work begins to illuminate the great potential of small molecule 20S proteasome activators to counteract multiple IDP-driven aspects of neurodegenerative disease pathogenesis.