Date of Award
1-23-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Protein misfolding and accumulation of misfolded species are associated with multiple neurodegenerative diseases, including Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD). α-Synuclein (α-Syn) misfolding and accumulation into Lewy bodies is closely linked to Parkinson’s disease. In ALS and FTD, TDP-43 and FUS are found to be aggregated in disease pathology. These proteins aggregate and associate with both a toxic gain of function of misfolded form and a loss of function due to misfolding. Therefore, it is critical to understand molecular mechanisms by which cells can prevent protein misfolding and how the cell can reverse the aggregation to develop new therapeutic strategies. HTRA1 is a PDZ serine protease ubiquitously expressed in the human brain. HTRA1 was previously shown to degrade fibrillar tau, which is associated with Alzheimer’s disease (AD). Further, HTRA1 mitochondrial homolog HTRA2 was suggested to implicate PD with inactivating mutations. In this dissertation, we investigated HTRA1 chaperone activity towards TDP-43 and FUS. We demonstrated that HTRA1, but not HTRA2, has inhibitory activity towards TDP-43 and FUS aggregation, though activity is most potent against α-Syn, highlighting that HTRA1 may be a therapeutic target for treating a range of neurodegenerative diseases. We demonstrated that the protease domain of HTRA1 is necessary and sufficient for inhibiting the aggregating of the substrates. Further, the HTRA1 chaperone activity is independent of its proteolytic activity. Additionally, we show that HTRA1 does not just inhibit aggregation, but also disaggregates preformed α-Syn fibrils through a proteolytically independent mechanism, which may promote their clearance. We further demonstrated that HTRA1-treated α-Syn fibrils render α-Syn seeding incompetent in mammalian biosensor cells. We investigated this mechanism through mass spectrometry, in which HTRA1 remodels α-Syn by specifically targeting the NAC domain, previously shown to be the critical domain driving α-Syn oligomerization and fibrilization. In a primary neuron model of α-Syn pathology, we show that HTRA1 and its proteolytically inactive form can detoxify α-Syn and prevent α-Syn hyperphosphorylation and accumulation, which are key pathological hallmarks of PD. This modulation of α-Syn also preserves cell viability. Taken together, we propose HTRA1 prevents aggregation and promotes disaggregation of α-Syn implicated in PD. This dissertation also evaluated HTRA1 chaperone's role in the cellular environment. Overexpression of HTRA1 or its proteolytically inactive form exerts a protective effect on α-Syn seeding, while knock-out of HTRA1 resulted in increased α-Syn aggregation in mammalian biosensor cells. Since HTRA1 is also secreted into extracellular matrix, we showed that the secretion of HTRA1 is not required for its chaperone activity in our cellular model. Overall, our results support HTRA1 has a native protection role against α-Syn aggregation with its chaperone function.
Language
English (en)
Chair and Committee
Meredith Jackrel
Committee Members
Gary Patti, Albert A Davis, Conrad C Weihl, Timothy Wencewicz
Recommended Citation
Chen, Sheng, "HTRA1 Prevents and Reverses α-Synuclein Aggregation, Rendering it Non-toxic and Seeding Incompetent" (2024). Arts & Sciences Electronic Theses and Dissertations. 3237.
https://openscholarship.wustl.edu/art_sci_etds/3237