Investigating the molecular environments and interactions of pathological TDP-43 filaments

Filamentous transactive response DNA-binding protein 43 (TDP-43) pathology characterises many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementias (FTD). Pathogenic mutations in TARDBP, the gene encoding TDP-43, can cause ALS and FTLD by increasing TDP-43 filament formation, demonstrating a central role of TDP-43 pathology in disease. TDP-43 pathology starts in focal sites in the central nervous system (CNS) and spreads to connected regions over time, which correlates with progressive neurodegeneration and clinical symptoms. There is growing evidence that TDP-43 filaments themselves may spread between neurons, potentially through axonal trafficking and synaptic transfer, and seed the assembly of native TDP-43, a phenomenon known as prion-like propagation. However, the underlying molecular mechanisms are largely unknown. An understanding of these mechanisms may yield therapeutic strategies to intervene with pathological TDP-43 filament formation to slow or prevent disease progression. In this thesis, I aimed to shine a light on these mechanisms by investigating the molecular environments and potential interactions of pathological TDP-43 filaments. First, I established novel human and murine neuronal model systems of stages of pathological TDP-43 propagation by incubation with exogenous TDP-43 filaments extracted from human brain. Second, I developed a time-resolved, antibody-targeted proximity labelling approach to map the molecular environments and potential interactions of pathological TDP-43 in these models at different stages of propagation in an unbiased manner. During the uptake of exogenous filaments, I observed an enrichment of distinct cell-surface receptors. At later stages, I detected an enrichment of specific chaperones and proteins involved in the endolysosomal system, intracellular trafficking, release and cellular degradation systems. Unexpectedly, I found that pathological TDP-43 filaments were most enriched at synapses, especially at the pre-synaptic active zone complex. I validated the presynaptic localisation of TDP-43 filaments in these models and in human tissue using immunofluorescence light microscopy, co-immunoprecipitation and synaptosome preparations. These findings suggest an important role for the pre-synaptic active zone complex in prion-like propagation of TDP-43 filaments and, possibly, resulting toxicity. During my PhD, I have mapped and validated novel molecular environments and potential interactions of pathological TDP-43 filaments at different stages of their prion-like propagation in novel neuronal models. These insights will guide future studies into the molecular mechanisms of propagation and may inform therapeutic strategies to intervene in this process.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2024

Author dc:creator

• Chen, Renren

Advisor dc:contributor.advisor

• Ryskeldi-Falcon, Benjamin

• TDP-43
• FTLD
• ALS
• Neurodegeneration
• Synapse
• Mass spectrometry

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/bf64f700-a91a-4616-a0f1-594b59d39d0a/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.113785

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/376619