Context-dependent Interactors Regulate TDP-43 Dysfunction in ALS/FTLD | JoVE Visualize

Area of Science:

Neuroscience
Molecular Biology
Genetics

Background:

TDP-43 protein dysfunction is a key feature in Amyotrophic Lateral Sclerosis (ALS), Frontotemporal Lobar Degeneration (FTLD), and Limbic-predominant Age-related TDP-43 Encephalopathy-neuropathologic Change (LATE-NC).
The precise mechanisms causing TDP-43 dysfunction, including its mislocalization and aggregation, are not fully understood.
Understanding TDP-43's cellular context and interactions is crucial for developing effective treatments for these devastating neurological disorders.

Purpose of the Study:

To investigate the context-dependent interactions of TDP-43 under conditions mimicking neurodegenerative disease pathology.
To identify novel proteins and pathways involved in TDP-43 mislocalization, aggregation, and functional loss.
To uncover potential therapeutic targets for TDP-43 proteinopathies.

Main Methods:

Utilized APEX2-driven proximity labeling coupled with mass spectrometry to map the TDP-43 interactome in specific cellular contexts.
Integrated single-nucleus RNA sequencing (snRNA-seq) data from ALS and FTLD patients to identify disease-relevant molecular alterations.
Performed functional screening to validate identified TDP-43 regulators and assess their impact on TDP-43 function.

Main Results:

Identified context-dependent interactors of TDP-43, revealing disrupted associations with splicing factors and altered biomolecular condensate dynamics.
Demonstrated that compromised nuclear speckle integrity, specifically via SRRM2 downregulation, promotes TDP-43 mislocalization and loss of function.
Discovered NUFIP2 as a TDP-43 interactor that sequesters the protein into cytoplasmic aggregates and co-localizes with pathology in patient tissues.
Highlighted HNRNPC as a critical regulator of TDP-43-mediated splicing, showing that modulating either protein can correct aberrant splicing events.

Conclusions:

Disrupted nuclear speckle integrity and altered protein interactions, such as with NUFIP2 and HNRNPC, are key mechanisms driving TDP-43 dysfunction in neurodegeneration.
The findings provide critical mechanistic insights into TDP-43 proteinopathies.
Identified specific proteins and pathways as potential therapeutic targets for ALS, FTLD, and LATE-NC.