RNA-mediated ribonucleoprotein assembly controls TDP-43 nuclear retention.

Area of Science:

• Neurobiology
• Molecular Biology
• Biochemistry

Background:

• TDP-43 (TAR DNA-binding protein 43) is crucial for RNA regulation and its mislocalization is implicated in neurodegenerative diseases.
• Maintaining TDP-43 within the nucleus is vital for its function and preventing cytoplasmic aggregation, a hallmark of diseases like ALS.
• Previous work showed RNA binding mediates TDP-43 self-assembly and phase separation via its N- and C-terminal domains.

Purpose of the Study:

• To investigate the role of TDP-43 self-assembly and macromolecular complex formation in its nucleocytoplasmic distribution.
• To understand how defects in RNA binding and phase separation impact TDP-43 localization and aggregation.
• To identify mechanisms controlling TDP-43 cellular homeostasis and potential therapeutic targets for TDP-43 proteinopathies.

Main Methods:

• Cellular imaging to observe TDP-43 localization and complex formation.
• Analysis of macromolecular complex size distribution in cells.
• Investigating the effects of mutations or conditions disrupting RNA binding and inter-domain interactions on TDP-43 assembly and localization.

Main Results:

• TDP-43 forms macromolecular complexes of varying sizes within cells.
• Impaired RNA binding or disruptions in inter-domain interactions, including phase separation, hinder the formation of the largest TDP-43 complexes.
• The formation of these large, RNA-mediated complexes is critical for retaining TDP-43 in the nucleus.

Conclusions:

• TDP-43's recruitment into large, RNA-dependent macromolecular complexes is a key mechanism for its nuclear retention.
• Size-dependent sequestration within these complexes prevents TDP-43 from entering the cytoplasm and forming aggregates.
• These findings elucidate fundamental pathways controlling TDP-43 cellular distribution and offer potential therapeutic strategies for TDP-43 proteinopathies.